The 'ACE' up their sleeves: Understanding NATO Agile Combat Employment

What is ACE? 

Agile Combat Employment (ACE) is the newest doctrine employed by NATO to enhance the ‘resilience and survivability’ of allied air operations. It combines ‘enduring’ and ‘contingency’ forward operating bases to posture capabilities and generate sustained combat air power through dispersal. This increases the flexibility of operations while creating ‘operational dilemmas’ for adversaries, complicating their targeting processes through dispersal. ACE’s agility comes from generating maximum combat effect with the minimum footprint, using ‘multi-capable airmen’ who fulfil a variety of roles beyond their specific trade to achieve this. ACE has been conducted by US and UK forces across Europe, the Middle East, Korea and Japan, testing and developing the doctrine, beginning to serve as a deterrent to aggressors and enhance NATO air power’s credibility, reflecting robustness and flexibility.

ACE speaks to the increased recognition throughout NATO of potential confrontation with near-peer adversaries, addressing concerns that adversaries might eliminate primary bases in the early phases of a conflict. ACE provides a ‘proactive and reactive operational scheme of manoeuvre’ to deter aggression and quickly respond to developing threats in contested air environments. Throughout the past twenty years, western air power has been an asymmetric advantage against non-state actors, enjoying air superiority almost by default, as air dominance above 20,000 feet was established soon after intervening in Afghanistan in 2001. Conversely, reviving the Cold War template of ‘dispersed operations’ reflects an attitude change, acknowledging the strategic shifts of the past decade, which include the scaling back of counterterrorism operations, the Ukraine war and Indo-Pacific tilt. The survivability of the Ukrainian Air Force in their ability to disperse aircraft and continue generating sorties confirms ACE’s utility.

ACE in Practice

In Britain, RAF and USAF units have begun to extensively practice ACE. Exercise ‘High Life’ in 2021 established the USAF’s ability to deploy multifaceted packages of tanker, intelligence and special operations aircraft, operating from non-standard bases. This has quickly evolved, as Exercise Astral Knight 23-6 saw six wings, comprising fighter, tanker, airlift and ground assets disperse from the UK, Germany and Italy to Finland and Lithuania. USAF F-22As and F-35As have deployed to Europe, using ACE to reposition contingencies to Romania and North Macedonia from Germany and Poland, training with local forces and providing assurance nations bordering high-tension, demonstrating the proactive and deterrent dimensions of ACE, signalling how NATO can surging capabilities at short notice to developing situations.

ACE has also seen real-world applications, bolstering NATO’s Enhanced Air Policing mission on its Eastern Flank. Through ACE, European airspace receives additional layers of security that can be reduced or heightened as situations develop, illustrating ACE already fulfilling its role. NATO air dominance is communicated to adversaries, ensuring assets are proactively dispersed in moments of high tension, maintaining the ubiquity of NATO air power and supporting smaller nations that are increasingly worried about NATO becoming complacent on security.

Exercise ‘Agile Pirate’ 2023 saw Typhoons and F-35Bs from RAF Coningsby and Marham deploy to MOD Boscombe Down, trialling dispersal for national defence purposes. Described as a ‘stepping stone’ to build knowledge and competency around ACE, this rehearsed the RAF’s ability to relocate Quick Reaction Alert capabilities, should primary bases become incapacitated. Smaller-scale manoeuvres like this ensure the national defence infrastructure’s integrity can be preserved amid potential crises. Frequently demonstrating these capabilities signals to adversaries how NATO is continually adapting to future challenges and capable of assuming operational advantages.

There are various tactics which ACE is exploiting to enable efficient generation of persistent air power. The RAF and USAF recently integrated to conduct the first hot-pit refuelling of RC-135 reconnaissance aircraft. Combat aircraft have typically made extensive use of hot-pitting (landing and refuelling without shutting down the aircraft), however, increasing the flexibility of atypical aircraft like this enables consistent generation of a variety of mission-sets should tanker resources become stretched, without necessitating long transits returning to fully prepared installations.

Future Challenges

The biggest challenges for ACE are the growing requirement to adapt to operate in the high north and identifying suitable base archetypes for adaptive basing. One solution identified is highway operations (using public roads as runways), which are already conducted by nations facing threats that might see their primary infrastructure weakened early in a conflict, such as Taiwan and across Scandinavia. Accordingly, Exercise Baana recently saw the first road take-off and landing trial by RAF Typhoons in Finland.

Historically, aircraft like the Avro Vulcan were optimised to operate to stringent airfield requirements. However, ACE activities so far have largely been limited to other prepared airfields, reflective of how modern military aircraft are restricted to operating from strong land surfaces, rarely incorporating unconventional operations into their design. This makes a major obstacle for the RAF and ACE the viability of dispersed, non-standard operations domestically. In the high north, experienced operators and a substantial availability of suitable locations with effective concealment make highway operations a lucrative option. In the UK, such archetypes are less prevalent, which limiting the RAF’s capacity to conduct this domestically. However, dispersal could still be achieved using prepared but unspecialised aerodromes in the UK, which was previously explored during an Agile Pirate exercise that saw Typhoons operate from Stornoway airport.

Strategically located civilian airports or former military airfields that maintain core airfield infrastructure (runways and parking areas), could provide additional options for domestic Typhoon ACE dispersal. This could be especially effective if the objectives are not sustained operations from these locations, but using these airstrips to conduct hot-pitting forward arming and refuelling, as practiced during Exercise Baana and has been carried out extensively by the USAF in similar trials.

Plans for highway operations also include the short take-off and landing (STOL) capabilities of the F-35B. There are few details around how this would occur, but several outlets suggest the use of aluminium AM-2 mats on highways up to 1,500 feet, in lieu of the requirement for heat-resistant material to safely operate the F-35B in STOL configuration. Despite this possible solution for the F-35, this reveals how future aircraft developments would benefit from integrating the ACE principles at the design stage.

During the Cold War, aircraft were designed considering similar principles, facilitating efficacy along the same objectives associated with ACE, particularly reactivity and flexibility. The B-52 Stratofortress is capable of a ‘cartridge start’, reducing the engine start period to ten minutes without extensive ground support equipment. This enables the bomber to ‘respond to threats at a moment’s notice’, aligning with the threat-timelines frequently discussed within ACE and reducing the aircraft’s operational footprint. Similarly, aircraft designed by SAAB have traditionally incorporated features specifically tailored to STOL, enabling highway and short runway operations in the high north, which the RAF is now trialling. With austere operations and rapid aircraft generation at the fore of ACE, considering similar design choices during future aircraft development enables ACE’s progression into an increasingly valuable doctrine.

In Conclusion

ACE is a critical move forward for NATO’s ability to respond to developing crises. ACE is becoming the favoured mechanism to tackle the ever-evolving challenges of the global security environment. It continues to be demonstrated effectively as it evolves to incorporate more elements, successfully demonstrating effectiveness when employed in real-world contexts. To fully reap the benefits of ACE, demonstrations of its application should be stepped-up, increasingly emphasising its proactive role to ensure ACE does not appear as occasional operations from different bases, instead signifying that NATO is on the front-foot. Through persistent ACE, NATO assumes an advantage by deterrence. To further develop ACE, its principles must be acknowledged throughout all stages of capability and doctrine development, ensuring that capabilities are best suited to contribute to operations with a minimum footprint and sufficient reactivity and flexibility.

The Freeman Air and Space Institute provides independent and original research and analysis of air and space power issues. Based in the School of Security Studies, the Freeman Institute places a priority on identifying, developing and cultivating air and space thinkers in academia and industry, as well as informing and equipping air and space education provision at King’s and beyond.