Queens and Princes: The Road Ahead for UK Carrier Aviation

 "The navy of any great power has the dream to have one or more aircraft carriers. The question is not whether you have an aircraft carrier, but what you do with your aircraft carrier."

- Major General Qian Lihua, director of the Chinese Defense Ministry's Foreign Affairs Office.

As it stands the UK is currently in the middle of a long process, which will culminate in the regeneration of key national capability: the ability to fly fixed wing aircraft from the decks of its carriers. Once this process is complete, some time in the early 2020s, the Royal Navy will return to operating full size carriers for the first time since Ark Royal, the last of the Audacious class, decommissioned in 1979. The new Queen Elizabeth class are true supercarriers, though not cast from the same mold as the US Navy's current Nimitz and Gerald R. Ford classes, they can still employ an impressive array of fixed and rotary wing aircraft. Although the class will be fitted with deck equipment for short take off and vertical landing (STOVL) aircraft like the F-35B, including the famous "ski-jump", they are of a similar size to the US Navy's former Forrestal and Kitty Hawk class carriers. It is easy to see that there is vast scope for modification and upgrade throughout their service lives, a process which every previous class of British carriers since the Second World War has undergone. The only certain thing is that these ships will end their service lives looking very different from the way they began them. Thankfully, unlike their predecessors, significant margins for growth have been built into the two ~70,000 ton ships from the start.

The short term shape of the carriers and their air groups is now mostly known, with the 2015 SDSR clearing up some of the speculation; especially with regards to the number of F-35B to be routinely embarked. The purchase of 42 airframes, with the specified purpose of arming the carriers with a "full air group", indicates that we could see the Tailored Air Group (TAG) routinely including an F-35B squadron; with a total of around 24 fixed-wing aircraft. This leaves a further 16 "slots" in the TAG available for a range of rotary wing assets, including the Army's Apache and the RAF operated Chinook. This is one of the most pioneering parts of the UK carrier concept: operating them as RN-led tri service assets. In theory these ships could simultaneously host RAF, Fleet Air Arm and Army Air Corps aircraft and maintainance crews. Making all this work in practice, in a challenging maritime environment, is likely to be a major test of the viability of the concept. It is encouraging that the tri service concept builds upon years of hard won experience, gained from the RAF/FAA Joint Force Harrier and the RAF/FAA/AAC Joint Helicopter Command. Small numbers of RAF Harriers have, in the past, operated from the decks of RN light carriers. As recently as 2011 the AAC flew some of its Apache gunships from HMS Ocean during the intervention in Libya. However, the scale of the Queen Elizabeth carriers and the sheer number of aircraft operating from her will inevitably complicate matters. Nevertheless, the concept is certainly exciting and will give the UK a truly flexible asset and a first class capability, if they can pull it off.

So, what might the future hold for these ships, the aircraft that fly from them and the people that will make the whole thing work?

"Jointness" and the Joint Strike Fighter:
As it stands the medium-term plan for the UK's fleet of F-35B Joint Strike Fighters has been spelled out. With the initial aircraft divided between the RAF's 617 "Dambusters" Sqdn. and the FAA's 809 "Immortals" Sqdn. Both of which will be based at RAF Marham in Norfolk, the UK hub for F-35. The pilots and maintainers in both squadrons will be a mix of RAF and FAA personnel, with the bulk likely being drawn from the RAF. The entirety of the UK F-35 fleet will also be officially "owned" by the RAF, this means that the RN will have a more limited degree of control over the FAA badged squadrons than in the past. Looking to history for a precedent for this sort of arrangement seems to throw up an eventual outcome that doesn't bode well for the current structure. Between 1924 and 1937 UK naval aviation was given over to a branch of the RAF, over the ensuing thirteen years a clear divide emerged between the naval aviators and their land based counterparts. While "FAA squadrons" will exist in the future structure they will, in effect, function as a naval branch of the RAF in all but name. Squadrons routinely deployed to the carriers, likely the FAA badged ones, will develop a more "naval mentality" and slowly diverge in skills and attitudes from those that do so far less frequently or not at all. While the planned common pool of pilots may seem like a way around this, it may in fact end up militating against the development of the skilled naval aviators necessary to get the most from the carriers.

Allowing some pilots, wearing light or dark blue uniforms, to spend much of their career conducting carrier operations at sea will eventually result in the slow re-emergence of a group of professional naval aviators that will not fit especially comfortably into the planned joint structure. The same could be said of the ground crews and maintainers, with certain people gravitating towards the naval environment and drafts on the carriers while others remain ashore. Whether this will eventually lead to a natural split in the joint force, with the navy taking control of some of the aircraft once the FAA rebuilds the necessary skills and personnel base to do so, remains to be seen. Although the cost of doing so for the RN will likely remain prohibitive. What is very much more likely is that de-facto divisions will emerge within the joint force, with the FAA badged squadrons containing the preponderance of experienced carrier pilots and "navalised" maintainers. The land-based squadrons' pilots will continue to qualify for carrier operations, but will likely spend less time at sea building up to the same levels of practical experience as their counterparts in the naval squadrons.

A USMC F-35B lands aboard the USS Wasp

Future of the air group:
The range of aircraft due to be flown from the decks of the Queen Elizabeth carriers in the medium-term is already clear at this point. The core of any TAG is always likely to be a number of F-35B to cover carrier air defence, strike and combat ISTAR. The number will vary depending on the task at hand, but I would think the ship would routinely deploy with a minimum of 12 on board-maintaining core naval aviation skills, providing CAP for the carrier group and allowing the ship to rapidly re-role for basic strike operations at very short notice. In the "maximum effort" scenario where both decks are in action simultaneously, with one acting as an enlarged LPH and the other a full strike carrier, I would still expect to see F-35B operating from both ships.
Merlin will form the second part of the core TAG, whether carrying the "Crowsnest" Airborne Early Warning (AEW) equipment, Anti Submarine Warfare (ASW) gear or in the HC3/4 cargo and troop transport configuration. What is reasonably certain is that Merlin, especially in the "Crowsnest" configuration, will nearly always be present aboard these ships.
The RN's Wildcats will also likely be a regular feature covering the surveillance, utility and surface strike (with the new Sea Venom lightweight anti-ship missile) roles. However, the limited number of airframes in RN service and high demand for the aircraft from other parts of the fleet, especially the forward-deployed escorts, may stand in the way of a regular presence on the carriers. The same case could be made for the ASW variant of the Merlin, the HM.2, with only 18 front-line airframes available to cover the needs of the escort fleet and the carriers. With regards to Wildcat best use of the tri service operations concept should be made by looking at close co-operation with the AAC, exploiting the possibility of routinely hosting of a number of Army Wildcats to ease the strain on the RN's fleet. This would also have the benefit of building and then sustaining the skills base necessary to rapidly and effectively embark and integrate Army helicopters and AAC crews at short notice if necessary.

Outside the core component aircraft of the TAG the carriers are also likely to see Army Apaches and RAF Chinooks embarked occasionally, on a less frequent basis. In order to operate these aircraft effectively from the carriers, pilots and aircraft will need to be exposed to the demands of operating in the maritime environment on a semi-regular basis. Similarly the ship-side aircraft handlers will need to build and maintain their experience dealing with very large helicopters such as Chinook. While it is helpful that both Apache and Chinook have already been deployed at sea, aboard HMS Ocean, the scale and tempo of deck operations aboard a carrier that will be simultaneously operating large numbers of helicopters and fixed wing aircraft will be very different. The RN is lucky that the basic needs of carrier operations, folding rotor blades and protection from salt corrosion, have already been built into the British Apaches. However, while Chinook does have the necessary corrosion resistance it lacks folding main rotors. Although the carriers' aircraft lifts have been designed to handle Chinook without folding blades these aircraft will take up a great deal of space in the hangar without them. This is acceptable if Chinook is only intermittently embarked for specific tasks. However, if it becomes a regular part of the air group then upgrading some or all of the Chinook fleet with powered folding rotors, or exploiting the unpowered folding mechanism already present, should be a high priority.

AAC WAH.64 Apache gunships operating from the deck of HMS Ocean

Looking slightly ahead into the next decade a single V-22 Osprey squadron should, if the money becomes available, be given serious consideration. The range of F-35B is already the shortest of all three variants, with forced loiter times an inherent part of carrier operations, air to air refueling (AAR) would be a very valuable support capability. The V-22 Aerial Refueling System (VARS) is a palletised probe and drogue tanking kit already in development for the US Marine Corps, for use with their F-35Bs. VARS initial operating capability is expected to be reached in 2017, so the system would be substantially de-risked in the event of a UK buy in the 2020s. While introducing a whole new aircraft and its supply chain into UK service would be costly, V-22 and VARS is the only realistic option open that is compatible with a STOVL carrier. With 16 airframes, for a squadron of 12 and a reserve of four, and eight VARS kits the UK could provide a continuous AAR capability for both carriers in the "maximum effort" scenario. The spare aircraft could also be flown from bases ashore to provide additional refueling capacity alongside the Voyager fleet during routine carrier operations, where only a single ship will be at sea. Of course, because VARS is a palletised kit, some of the aircraft could also be used in the heavy lift and troop transport roles for which they were originally designed; freeing up RAF Chinooks for operations ashore. The Osprey would also be able to cover most of what the US Navy calls the "Carrier Onboard Delivery" (COD) role, moving personnel and stores long distances from ship to shore and vice versa. Although the V-22 lacks the cargo space to carry the Pratt & Whitney F-135 engine for the F-35, it's range and carrying capacity are still impressive. It seems to be the case anyway that in RN service the spare engines will be carried by the accompanying MARS solid support ship: able to transfer them to the carrier via their heavy RAS gear when needed. So the Osprey's lack of capability in that area wouldn't be a severe drawback. Overall the V-22 would be a very useful option to add to the Queen Elizabeth carriers' TAG if, in future, the money becomes available.

A USMC V-22 Osprey refueling an F-18 with the VARS drogue

Another interesting area for future development will be the operation of short takeoff and landing drones. A number of the current generation of propeller-driven long endurance UAVs operate at low enough speeds to consider carrier operations without catapults a serious proposition. A naval version of the Watchkeeper surveillance drone, or simply using some of the Army's could be one possibility for an initial round of trials to prove the concept. If successful, it could pave the way for trials with larger UAVs such as Predator, possibly using a simple pneumatic catapult for launch. All this is, however, a long way off. Although proving the concept and clearing the carriers to operate larger surveillance drones than the RN's ScanEagle would certainly be something to investigate and develop in the medium term.

Overall, by the time the Queen Elizabeth carriers reach their full operating capability in the mid-2020s the RN will have a pair of very capable ships with robust air groups, able to be tailored to suit specific missions. While the phrase "second only to the United States" is so often repeated by MoD and government officials that it's become a bit of a cliché, the capability offered by the Queen Elizabeths will almost certainly live up to those ambitious words. There are ways that this impressive capability could be further enhanced, with V-22 for AAR, heavy lift and COD, and grown over time by trialing UAVs; with a view to eventually including them in the array of aircraft that can be operated from the carriers' decks. If the TAG concept is properly implemented and a variety of aircraft from the RAF, FAA and AAC are routinely embarked for training in the maritime environment then these ships will deliver on the impressive flexibility they were designed to offer.

Operating both carriers:
SDSR 2015 delivered the pledge that the UK would operate both ships simultaneously to ensure one carrier will always be available for deployment 24/7/365. What this will mean in practice is that most of the time one ship will be alongside in the UK, usually undergoing repairs or a refit, while the other acts as the duty carrier: available to respond to events and deploy at short notice. However, as the RN discovered with its previous carriers, leaving ships alongside with minimal manning for prolonged periods of time leads to steady material deterioration and shortens the lives of the ships. Both Invincible and Ark Royal fell afoul of this, spending significant time unmanned and alongside in 3 Basin badly effected the material state of both ships. With only two Queen Elizabeth carriers available the RN cannot afford to make the same mistake, effectively mothballing one ship at a time for lack of crew will shorten the life of a class that could, given adequate care, serve for half a century. Failure to properly man and service both ships at all times would inevitably impose avoidable maintenance costs further down the line and steadily erode the RN's ability to surge two carriers as a "maximum effort" as a serious war fighting contingency against a near-peer opponent.

An Invincible Class carrier, tied up alongside in HMNB Portsmouth's 3 Basin

It has been said elsewhere but the 2020 SDSR needs to include a substantial increase in RN manpower, to enable the service to adequately crew both ships at all times and surge two carrier decks in an emergency: provided the spare ship isn't in deep refit. Providing adequate crew for both ships would also introduce additional opportunities for training in or near UK waters. The need to provide the RAF and AAC pilots and maintainers with experience of operating in the maritime environment has already been mentioned. With only one carrier deck operating at any time, which may be away on operations, the limited availability of a ship for the component elements of the TAG to train on is concerning. The flexible TAG concept only works if its constituent elements can be called upon at short-notice to form a mission-specific package. While the mock carrier at RNAS Culdrose will be a useful facility for training pilots in deck operations, it is no substitute for realistic training at sea. With a sufficiently manned second ship the RN could, when the ship is available, use the reserve carrier for training around the UK. Employing the Queen Elizabeths in this way ensures that the RN would always have more than enough ship-side crew to keep the duty carrier at full strength, and enough to make the two carrier "maximum effort" a realistic prospect. In order to achieve this though, the RN's total manpower must rise.

CATOBAR:
Finally, the thorny issue of whether these ships will ever be reconfigured and refitted with catapults and arrestor wires needs addressing. In 2012 the Coalition government looked at the costs of converting both ships, briefly committing to the cat & trap configuration, before reverting to the original STOVL configuration once it became clear that the costs of conversion would be prohibitive. The cost of converting the partially built Prince of Wales was stated to be an additional £2bn, while the class was supposed to be relatively easy to change from STOVL to CATOBAR in reality this does not seem to be the case. Some sources stated at the time the decision was reversed that conversion would have required modifications to over 200 compartments. A mid-life conversion may become necessary if there is no available STOVL replacement for F-35B after its 2045 out of service date. With so many unknowns inherent in predicting what could happen thirty years into the future, all that can be done is to restate much of what we already know.

The QE Carrier flight deck in both the STOVL and CATOBAR configurations

A CATOBAR conversion would be extremely expensive, it would involve very extensive rebuilds of the ships and the generation of a whole new set of training pipelines for pilots, flight controllers and deck crew. It would also mean learning a whole new way of doing things, and it could not be done cheaply or quickly. When all is said and done developing a bespoke UK STOVL aircraft to replace the F-35B might actually end up being the cheaper option, when compared with the cost of the substantial organisational changes that would be necessary. While many long time supporters of the Royal Navy's cause would, no doubt, love to see the UK return to catapult carrier operations the reality is that STOVL currently offers an effective capability at a tolerable cost. In the author's opinion the decision to convert to CATOBAR would only be taken if there was no other alternative, including the development of a bespoke UK STOVL aircraft. The hope at this point should be that the USMC continues to make a convincing case for STOVL aviation within the US armed forces and ultimately gets a like for like F-35B replacement. This would enable the UK to participate in a joint or multilateral programme, with orders large enough to drive down the unit cost. It must be stated again though that predicting the shape of UK naval aviation that far into the future is almost impossible. For all the sentimental and symbolic importance attached to CATOBAR, it is clear at this point that while a mid-life conversion would be possible, it is far from preferable.

Almost from their very inception the Queen Elizabeth class carriers have proved be a subject of controversy. Fierce and sometimes public debates have been held on their relevance in the modern world, usefulness for the UK and the difficulties involved in realising their potential capabilities in practice. The last point was expressed with a clarity that only tabloid journalism could manage in the oft-repeated phrase "carriers with no aircraft". Thankfully, it is now clear that the tabloids were wrong and the public's concern was partly misplaced, the carriers will have a robust TAG with a great deal of potential flexibility and, if necessary, striking power. While there is still a little room for improvement with regards to the air group such as the inclusion of an AAR tanker, Osprey VARS or otherwise, the concept is sound and the aircraft will be available to start realising it by the early-mid 2020s. While the author still has concerns over the long-term durability of the Joint RAF/FAA F-35B arrangement it is certainly a workable plan and may yet prove to be a success. The key to successfully realising the high-minded goal of turning the carriers into tri service aviation ships will be regular joint training for all component parts of the TAG, on the mock carrier deck at RNAS Culdrose but, more importantly: at sea. Without experience and training on a real carrier deck the individual TAG components will likely struggle to adapt to a very different working environment whilst also trying to conduct operations. The old adage train how you fight comes to mind, if we intend to embark RAF Chinooks and F-35s or AAC Apaches and Wildcats then they must spend regular time training aboard one of the carriers. In order to achieve this the RN needs to be given the manpower to operate both carriers simultaneously as often as repair and refit schedules will permit, with the off-duty carrier operating near the UK as a training platform. This would have the added benefit of keeping both ships out of what would effectively be time spent in mothballs: alongside in Portsmouth with a caretaker crew aboard, which shortened the lives of the preceding Invincible class. If the UK intends to make good on it's substantial investment in the Queen Elizabeth carriers they need to be manned sufficiently to maintain them over their 40-50 year lifespan, failure to do so would be yet another example of the MoD being "penny wise and pound foolish".
Finally, while a post-F-35B conversion to the catapult and arrestor wire configuration is theoretically possible, the costs of doing so, and the institutional upheaval it would cause, would be enormous. In the end, despite the emotional pull exerted by the idea of "proper" carriers and the drama of catapult operations, a CATOBAR conversion should only be embarked upon if the only other alternative is scrapping the ships prematurely and wasting the money already sunk into them.

While some commentators have been very dismissive of the UK carrier programme in the author's opinion they could, in time, give the UK a truly first-class capability "second only to the United States". However, in order to achieve that ambitious and, let's not forget, thoroughly attainable goal the UK needs to make good on its current investment in the carriers. This can be achieved by manning and operating both, potentially investing in AAR capability and most importantly ensuring all component parts of the TAG regularly embark and train on the carriers. At the close I will return to the words of Major General Lihua:

 "The question is not whether you have an aircraft carrier, but what you do with your aircraft carrier."

Roadmap to Victory: Defeating the Islamic State

The factors which make Islamic State relatively straightforward to contain geographically are the same ones which make it nearly impossible to drive them from the lands they currently occupy. The group relies upon the often irreconcilable divisions between their enemies in order to survive, these divisions allow them to face each of their enemies  on the ground in turn. I would suggest that the nightmare scenario for ISIS commanders, many of whom are experienced military men, is a war on multiple fronts. IS puts little stock in static defence, probably based on the assumption that to spread it's forces thinly along its borders would invite disaster. They realise that, in the words of Frederick the Great, "he who defends everything, defends nothing". It also tells us that the likelihood is that their army isn't nearly as large as some commentators suggest, they do not have experienced troops to spare for defensive action. Instead their strategy is to lightly defend their external borders. Using very small numbers of troops, suicide bombers and booby traps to harass and slow down their enemies. Importantly they do not attempt to blunt their attacks by fighting significant defensive actions. Again, they are probably right to do so. They likely judge that defending territory, even urban areas, in the face of Coalition air power is ill advised at best and suicidal at worst. Any fight where ISIS forces become pinned in place by enemy ground troops for more than a few days will likely result in disproportionate losses for the Islamic State, as the full weight of Coalition air power is brought to bear. We saw this happen when IS conducted protracted offensive action around Kobane. The experience of heavy losses in that battle: ~2000 fighters killed, an unknown number injured and 18 tanks destroyed, likely shaped their current mode of conducting operations. Their commanders understand that pushing against enemy strength, along a single axis, in order to seize an objective won't work. Instead they attack where their enemies are weakest. Short sharp offensives that take (or retake) ground at a low cost in the lives to their base of experienced fighters. By always holding the initiative, and an element of surprise, they continue to dictate the terms of the ground war; even when their enemies are on the offensive.

While the group is committed to a strategy of continued offensive action, which keeps their enemies off balance and prevents them from gathering the forces for a decisive thrust into the Islamic State itself, it has not been able to repeat it's initial rapid advances. This is almost certainly because they are constrained, like all the other warring factions, by their inability to operate effectively outside areas populated by their own ethno-religious group. It's probable that one reason for their initial gains in Iraq was Islamic State's ability to exploit the human landscape in Sunni majority areas far more effectively than their opponents in the Shia dominated Iraqi army. This factor makes them far easier to contain territorially, because the same factor which enabled them to expand so quickly into the Sunni parts of Iraq now works against them when they try to advance into Shia or Kurdish majority areas. Containing the group in Sunni areas of Iraq and Syria has drawbacks though. In order to maintain the appearance of continuous offensive success they have begun parallel strategies of terror attacks on the West and the establishment of franchises outside their main territory.

There are several important things we can infer from their behaviour, which will be essential in formulating a strategy to defeat them militarily.

1. Contrary to their own narrative they are acutely aware that they cannot sustain heavy casualties. This has led them to avoid protracted offensive action and to all but abandon the defensive as a viable option.

2. Their veteran field army is vital to their strategy, as it enables them to conduct effective offensive action. This prevents their enemies from concentrating enough force along a few axies of attack to seriously threaten their territory.

3. Their inability to make headway in non Sunni areas, south towards majority Shia Baghdad and North into Kurdish territory, is a product of the same forces which prevent Kurdish or Shia dominated Iraqi forces from making headway in the opposite direction. All the forces present in Iraq lack the ability to project their military power into areas controlled by different religious and ethnic groups, ISIS included.

4. ISIS rely on the divisions throughout the region and beyond it for their survival against conventional military intervention with ground forces. ISIS leaders likely know that the US will continue to veto Turkish intervention on the basis that it will likely be directed as much against their Kurdish allies as against IS. Many of the Gulf States and Saudi Arabia seem content to watch as Assad's Iranian ally is drawn ever deeper into the Syrian quagmire. Of course it goes without saying that Assad and the Free Syrian Army will continue to battle one another far more intensely than ISIS.

5. Containing IS is likely pushing the group to adopt a new strategy, which includes acts of international terrorism and spreading franchise groups, in order to maintain the appearance of effective offensive action.

The ISIS field army is at the core of their strategy of continuous offensive action.

With these deductions in mind, what would an effective strategy for defeating ISIS look like? Any such action would have to start with the premise of destroying, or so badly damaging, their field army that they cease to be capable of conducting meaningful offensive or counter offensive action. This is far easier said than done, Western troops would not be able to achieve this. The leadership of IS will undoubtedly have prepared contingencies for the introduction of conventional forces by a major military power. Their reaction would probably be to immediately disperse their forces and adopt a purely guerilla strategy of protracted resistance. This is unappealing because it makes the wholesale destruction of their trained manpower base a near impossibility over any acceptable time span. In order to be drawn into a conventional battle IS commanders must believe that they stand a reasonable chance of success. This means the main ground component will have to be drawn from at least one, but likely more, of the factions currently fighting on the ground.

The fight to destroy IS' army cannot be a defensive action on the part of their enemies, so long as IS hold the initiative they remain free to break off costly offensive action and refocus their efforts elsewhere. Their army needs to be drawn into a battle they patently do not wish to fight, a protracted static defensive action, where coalition air power can be fully brought to bear against them. IS will not be forced to commit to such an action easily. It would probably require a land force threatening one of their major centers of power, Raqqa or Mosul, in order to force them to commit to a static defensive action in a single location. Their leaders will almost certainly understand the difficulty of assaulting a city filled with determined defenders and calculate that they stand a reasonable chance of success. In an action against dug in ISIS forces holding a major city, coalition members must set aside many of their reservations about conducting strikes in urban areas. Civilians will die and IS may seek to keep as many of them in place as possible, to limit the effectiveness of air power by exploiting the squeamishness of Western populations when it comes to unintended collateral damage. Embedding forward air controllers with trustworthy local forces such as the Peshmerga would be one way to reduce civilian casualties and increase the effectiveness of coalition air strikes.

We must seek to turn one of these cities and it's surrounding areas into a "Stalingrad" for ISIS, pushing them to the point where they commit totally to a symbolic battle  in which their army can be irreparably damaged; by inflicting severe losses on their base of experienced fighters. If IS refuse to deviate from their existing strategy, instead opting to avoid defensive action altogether, then they will lose control of one of their major power centers effectively without a fight. That would be a major propaganda coup for their enemies and deprive them of a substantial portion of their economic base and manpower pool. Putting ISIS between a rock and a hard place in this manner can be no bad thing, but I would expect there to be a good chance of them standing and fighting in place. To avoid such a battle would utterly shatter their aura of invincibility.

Of the two options Raqqa is by far the less attractive target. Situated deep within ISIS held territory in Syria, it would probably require a united Syrian force to successfully threaten it and then force IS into a defensive battle. Seeing as there is no real prospect of such a force existing in the near future, Raqqa must be discounted as currently unfeasible. That leaves us with only one real option: Mosul.

Mosul, surrounded on three sides in the Northeast by Kurdish forces.

Recent Kurdish operations have been focused on the corridor linking ISIS held territory in Eastern Syria to it's Iraqi stronghold in Mosul, with the town of Sinjar falling to a joint YPG/PKK and Peshmerga offensive aided by Yezidi militias earlier this month. In accordance with IS' current strategy, the area was not seriously contested, with estimates of around 700 fighters facing off against over 7,500 Kurdish troops. Even the Kurdish threat to and eventual capture of the logistically important Highway 47 did not force IS to commit it's main strength to the battle. As I've previously outlined I believe that IS will only commit itself to a defensive battle if one of their two major population centers are threatened.

The next question which requires addressing is do the Kurdish forces have the will and the capability to conduct such an operation? Clearly convincing the Kurds to engage their forces in a bloody urban battle of attrition, outside their own territory, will be a significant task. In this respect the West at least has it's track record of long standing friendship and co-operation to build upon. ISIS control of Mosul also presents a clear threat to Kurdish territory, acting as their primary base of operations in Northern Iraq. Kurdish leaders and commanders likely understand that sooner or later Mosul will have to be retaken, although their current hopes are probably that such a significant task could be left to the better equipped Iraqi Army to deal with at a later date. However, the now Shia dominated Iraqi Army has repeatedly displayed a profound unwillingness to advance into Sunni majority areas. It's front line is also ~180km further from Mosul than the Kurds, any advance towards Mosul on the part of the Iraqi Army would have to take a lot of time clearing the surrounding areas of resistance. This sort of action would also likely provoke a major attack from ISIS elsewhere, potentially in Anbar province, as they did earlier this year in order to preemptively blunt a similar northward offensive. An advance by the Iraqi Army would therefore be most likely to succeed if it were to fall after ISIS had committed their main strength to Mosul, removing the potential for a major offensive elsewhere. Convincing the Kurds to undertake a major offensive against Mosul would be difficult, but not impossible as part of a multi front offensive involving the Iraqi security forces.

More important than the Kurds willingness to conduct an offensive against Mosul is their military capacity to do so. If they lack the necessary military resources to undertake an operation of this scale and complexity then the plan is a non-starter.

Estimates on the military resources ISIS commands range from the CIA's conservative 2014 estimate of 31,000 fighters to the Kurds own claims of a force 200,000 strong. More recent reports from 2015 suggest that IS can call upon a force in the region of 40,000 fighters, although it is unclear what proportion of these are tied to garrison and rear echelon duties. Western troops usually require a ratio of 3-1 support to combat troops, but let us err on the side of caution and suggest that the ratio for ISIS is far lower. For the purpose of this exercise I will assume that a third of their troops would be unavailable or unsuitable for combat duties, meaning they can muster 2 combat troops for every fighter engaged in supporting activities. This gives them an estimated total strength of around 25,000 fighters. Their heavy equipment varies wildly in quality and age but IS is thought to have around 170 tanks, 150 armoured personnel carriers and a few hundred armoured cars. These numbers must come with the caveat that they are old, likely out of date, and certainly far higher than the strength they could actually deploy.

The estimated number of troops available to the Peshmerga varies wildly, ranging from 80,000 and 200,000. Accurate figures are difficult to come by but a conservative estimate would be that they command around 120,000 troops with a much greater proportion dedicated to rear echelon and garrison duties than IS. For the sake of argument let's say the Peshmerga can field one fighter for every two supporting troops.  This would produce a theoretical force of ~40,000 front line combat troops. The YPG and other allied militias could provide a few thousand more, but their equipment and is generally insufficient for much beyond the guerrilla or light infantry duties at which they admittedly excel.

While the raw numbers, although sketchy, suggest that the "Kurdish forces" do have a numerical advantage over IS; the numbers alone hide a range of issues that prevent the Kurds from putting such a force in the field. Firstly the political divisions within the Peshmerga are a major stumbling block, the 36 brigades are all independently controlled and many are aligned with the PUK, KDP and KRG factions. Although there have been efforts to unite these forces under a single unified command to fight IS, progress has so far been slow. Similarly, these politically divided brigades often struggle to cooperate with one another. Heavy equipment is another area where the Peshmerga has weaknesses. They actually do possess a sizable number of armoured vehicles and heavy artillery pieces, mostly ex - soviet, seized from the Ba'athist army's stockpile during the 2003 Iraq war. In total the Peshmerga have over 500 tanks and around 200 armoured personnel carriers. The lack of spare parts and ammunition, however, prevents most of it from being made available for front line use. Another problem is that, for the size of their forces, their logistical support structures are woefully inadequate. Conducting protracted offensive action will absolutely require a far more robust and effective logistics network backing it up.

Kurdish T-55 tanks: available in numbers but lacking vital spare parts 

Several of the highlighted areas of weakness can be remedied with outside help. Russia's recent commitment to directly combating IS makes the task of sourcing spares and ammunition for much of the Peshmerga's heavy equipment a more straightforward exercise. If the Russians refuse to cooperate then all of the required parts and ammunition are still readily available on the international market, but accessible only to state buyers. The US Army has over 30,000 M939 utility trucks currently set for disposal, transferring a portion of these to the Kurdish forces would go a long way towards solving some of their logistical problems. Importantly both these solutions avoid arming the Kurds with modern equipment that would allow them to challenge Iraqi government forces at a later date, supplies of ammunition and spare parts could easily be cut off after the conflict, to limit their potential for armed secession.

The politicised nature of many of the Peshmerga brigades, and lack of a unified command structure, are far more intractable but not insurmountable problems. Significant but slow progress has been made towards a unified Peshmerga command structure, a series of defeats and blunders fighting IS has made it clear that a more unified effort will be necessary to successfully combat ISIS. I would advise that if the Kurdish regional government manages to implement a functional unified command structure then the West should equip them with the spare parts and ammunition they need to deploy their existing heavy equipment and take the fight to IS around Mosul. If it is made clear that supplies will only come once the Kurds implement a workable unified command it could give the initiative the impetus it needs to be put into place.

The Peshmerga would very likely have an overall and local numerical advantage over IS, especially considering that the Islamist group would be taking an enormous risk if it concentrated a very large portion of it's strength on the defence of Mosul. As Operation Free Sinjar has demonstrated, the Kurds do seem able to concentrate the large forces necessary to execute complex urban assault operations. A battle for control of Mosul would be on an entirely different scale however, without their heavy equipment and a unified command it would be an enormously risky and costly undertaking; even with the Iraqi Army moving up from the south. It does, however, remain the best possible chance for anti-IS forces to inflict irreparable attrition to their trained fighters and prestige.

In summary, IS is militarily easy to contain. The difficulty lies in dislodging them from the territory they hold because of their strategy of harassment rather than static defence and continuous offensive action directed against their enemies weakest points. Despite this, I believe their commanders are acutely aware that their strategy would collapse if they were to lose enough of the trained field army to prevent their offensive action from being successful. This cannot simply be achieved by blunting their offensives, leaving them free to withdraw at will and attack elsewhere. In order to inflict the necessary damage they must be forced into conducting a static defensive battle that they do not wish to fight. The only way of doing this, in the author's opinion, is by seriously threatening one of their two major centers of power: Mosul or Raqqa. As there are currently no forces on the ground capable of conducting an offensive towards Raqqa, Mosul is left as the only realistic option open to us. While the Iraqi army is the better equipped force, they will remain unable to concentrate the force to advance northwards with IS threatening their flank in Anbar province. It will therefore have to be the geographically closer Kurdish forces which initiate the battle and begin the process of drawing IS reserves into the city before the Iraqis can advance, certain that those reserves couldn't be employed for offensive action against their Western flank. In the meantime the West needs to help the Kurdish forces build the logistical support structures necessary for them to conduct protracted offensive. The West must also seriously encourage the establishment of a functional unified command, possibly using the delivery of spare parts and ammunition for their existing heavy weapons as an incentive to do so.

Defeating IS is a matter of making their current military strategy for Iraq and Syria unworkable. This can only be achieved by forcing them to fight a battle that will result in the fatal degradation of their fighting power. I believe an attack on Mosul, coordinated in the manner I have laid out, could achieve this without the need for large Western conventional forces.