Allied Command Operations (ACO)

  • Last updated: 11 Nov. 2014 10:54

Allied Command Operations (ACO) is responsible for the planning and execution of all Alliance operations. It consists of a small number of permanently established headquarters, each with a specific role. The Supreme Allied Commander, Europe - or SACEUR – assumes the overall command of operations at the strategic level and exercises his responsibilities from the headquarters in Mons, Belgium: the Supreme Headquarters Allied Powers Europe, more commonly known as SHAPE.


  • ACO, located at SHAPE in Mons, Belgium, is responsible for the planning and execution of all NATO military operations.
  • The command’s aim is to maintain the integrity of Alliance territory, safeguard freedom of the seas and economic lifelines and preserve or restore the security of its members.
  • ACO is one of two strategic commands at the head of NATO’s military command structure.
  • It consists of a small number of permanently established headquarters operating at the strategic, operational and tactical levels.
  • It is headed by the Supreme Allied Commander Europe, or SACEUR, who exercises his responsibilities from SHAPE.

ACO is one of two strategic commands at the head of NATO’s military command structure; the other is Allied Command Transformation (ACT), which as its name indicates, leads the transformation of NATO’s military structure, forces, capabilities and doctrine. Together they form what is called the NATO Command Structure (NCS), whose function is first and foremost to be able to address threats and should deterrence fail, an armed attack against the territory of any of the European¹ Allies. Ultimately, the NCS plays an essential role in preserving cohesion and solidarity within the Alliance, maintaining and strengthening the vital transatlantic link and promoting the principle of equitable sharing among Allies of the roles, risks and responsibilities, as well as the benefits of collective defence.

ACO must ensure the ability to operate at three overlapping levels: strategic, operational and tactical, with the overarching aim of maintaining the integrity of Alliance territory, safeguarding freedom of the seas and economic lifelines, and to preserve or restore the security of NATO member countries. Moreover, in the current security environment, deploying forces further afield has become the norm.

Decisions to streamline NATO’s military command structure were taken in June 2011 as part of a wider process of reform. ACO was principally affected by this reform, the full implementation of which is expected by the end of 2015, when all entities involved will reach full operational capability.

With this reform, new tasks stemming from the 2010 Strategic Concept were included and the Alliance’s level of ambition maintained. Elements of ACO will gain in flexibility and provide a deployable Command and Control (C2) capability at the operational level, offering choices and options for rapid intervention that have not previously been available to the Alliance. Moreover, a Communication and Information Systems (CIS) Group has been formed as part of the military command structure to provide additional deployable communication and information systems support. Once fully implemented, the reform will lead to an estimated reduction in personnel of approximately 30 per cent (from 13,000 to 8,800). The military command structure proper has been downsized from 11 entities to seven².

Links with the NATO Force Structure will be reinforced. The Force Structure is composed of Allied national and multinational deployable forces and headquarters placed at the Alliance’s disposal by member countries on a permanent or temporary basis. National contributions are made available for NATO operations at appropriate states of readiness when required. Rules of deployment and transfer of authority to NATO command can vary from country to country.

  1. It is considered that whereas Article 5 applies to the entire NATO Treaty Area, the NATO Command Structure’s operational area of responsibility does not include the territory of the United States or Canada. This is not meant to imply that the NATO Command Structure should not be able to support the United States and Canada should the territory of these two Allies be subject to an armed attack, but rather to acknowledge that defensive operations on the territory of these two Allies will be conducted, commanded and controlled in accordance with bilateral arrangements and not under the auspices of the NATO Command Structure.
  2. These figures cover Allied Command Operations and Allied Command Transformation.
  • The military command structure

    As previously explained, ACO is a three-tier command with headquarters and supporting elements at the strategic, operational and tactical level. It exercises command and control of static and deployable headquarters, as well as joint and combined forces across the full range of the Alliance’s military missions. Joint forces are forces from two or more military departments working under a single command and combined forces are forces from different countries working under a single command.

    SHAPE, at the strategic level, is at the head of six operational commands, two of which are supported by tactical (or component) level entities.

    Allied Command Operations

    Strategic level command: SHAPE

    SHAPE is a strategic headquarters. Its role is to prepare, plan, conduct and execute NATO military operations, missions and tasks in order to achieve the strategic objectives of the Alliance. As such it contributes to the deterrence of aggression and the preservation of peace, security and the territorial integrity of Alliance.

    ACO is headed by SACEUR, who exercises his responsibilities from SHAPE. Traditionally, he is a United States Flag or General officer. SACEUR is dual-hatted as the commander of the US European Command, which shares many of the same geographical responsibilities. SACEUR is responsible to the Military Committee, which is the senior military authority in NATO under the overall political authority of the North Atlantic Council (NAC) and the Nuclear Planning Group (NPG). The Military Committee is the primary source of military advice to the NAC and NPG.

    Operational level commands: Brunssum and Naples

    The operational level consists of two standing Joint Force Commands (JFCs): one in Brunssum, the Netherlands, and one in Naples, Italy. Both have to be prepared to plan, conduct and sustain NATO operations of different size and scope. Effectively, they need to be able to manage a major joint operation either from their static location in Brunssum or Naples, or from a deployed headquarters when operating directly in a theatre of operation. In the latter case, the deployed headquarter is referred to as a Joint Task Force HQ or JTFHQ and should be able to operate for a period of up to one year.

    When deployed, a Joint Force Command is only charged to command one operation at a time. However, the elements of the Joint Force Command which have not deployed can provide support to other operations and missions. When a Joint Force Command is not deployed, it can assist ACO in dealing with other headquarters which are deployed in theatre for day-to-day matters and assist, for instance, with the training and preparation for future rotations.

    The two commands at this level are also responsible for engaging with key partners and regional organisations in order to support regional NATO HQ tasks and responsibilities, as directed by SACEUR. Additionally, they support the reinforcement of cooperation with partners participating in NATO operations and help to prepare partner countries for NATO membership.

    Tactical level commands: Izmir, Northwood and Ramstein

    Land, maritime and air commands

    The tactical (or component) level consists of what is called Single Service Commands (SSCs): land, maritime and air commands. These service-specific commands provide expertise and support to the Joint Force Commands at the operational level in Brunssum or Naples. They report directly to SHAPE and come under the command of SACEUR.

    • Land command, Headquarters Allied Land Command (HQ LANDCOM), Izmir, Turkey: this command’s role is to provide a deployable land command and control capability in support of a Joint Force Command running an operation larger than a major joint operation. It can also provide the core land capability for a joint operation (major or not) or a deployable command and control capability for a land operation. Izmir is also the principal land advisor for the Alliance and contributes to development and transformation, engagement and outreach within its area of expertise.
    • Maritime command, Headquarters Allied Maritime Command (HQ MARCOM), Northwood, the United Kingdom: this command’s role is to provide command and control for the full spectrum of joint maritime operations and tasks. From its location in Northwood, it plans, conducts and supports joint maritime operations. It is also the Alliance’s principal maritime advisor and contributes to development and transformation, engagement and outreach within its area of expertise. Northwood is ready to command a small maritime joint operation or act as the maritime component in support of an operation larger than a major joint operation.
    • Air command, Headquarters Allied Air Command (HQ AIRCOM), Ramstein, Germany: this command’s role is to plan and direct the air component of Alliance operations and missions, and the execution of Alliance air and missile defence operations and missions. Ramstein is also the Alliance’s principal air advisor and contributes to development and transformation, engagement and outreach within its area of expertise. Ramstein, with adequate support from within and outside the NATO Command Structure can provide command and control for a small joint air operation from its static location, i.e., from Ramstein or can act as Air Component Command to support an operation which is as big or bigger than a major joint operation.

    To reinforce its capability, Ramstein has additional air command and control elements available: two Combined Air Operations Centres and a Deployable Air Command and Control Centre. The air elements are also structured in a more flexible way to take account of the experience gained in NATO-led operations.

    Additional air support

    To carry out its missions and tasks, HQ AIRCOM (Ramstein) is supported by Combined Air Operations Centres (CAOC) in Torrejon, Spain and in Uedem, Germany, as well as one Deployable Air Command and Control Centre (DACCC) in Poggio Renatico, Italy.

    • CAOCs: both the CAOC in Spain and in Germany are composed of two parts. One part is a Static Air Defence Centre (SADC) responsible for air policing and the other, a Deployable Air Operations Centre (D-AOC), which supports operations. The D-AOC is an element focused on the production of combat plans and the conduct of combat operations. It has no territorial responsibilities assigned during peacetime, but supplements the HQ AIRCOM when required.
    • DACCC: this entity based in Italy consists of three elements. Firstly, a DARS or Deployable Air Control Centre + Recognized Air Picture Production Centre + Sensor Fusion Post. The DARS is responsible for the control of air missions including surface-to-air missiles, air traffic management and control, area air surveillance and production of a recognised air picture and other tactical control functions; secondly, a D-AOC, which has the same role as a CAOC; and thirdly, a Deployable Sensors Section, which provides both air defence radar and passive electronic support measures tracker capabilities that are deployable.
    Communication and information systems  

    Communication and information systems (CIS) have been split into two: the deployable CIS capabilities and the static CIS capabilities.

    The NATO CIS Group based in Mons, Belgium will provide deployable communications and information systems support for ACO. The NATO CIS Group is responsible for the provision of all deployable CIS capabilities, as well as CIS operations and exercises planning and control. It acts as the coordinating authority for command and control services support to operations. The provision of the static and central CIS capabilities is the responsibility of the NATO Communications and Information Agency (NCIA), which is not part of the NATO Command Structure.

    The NATO Communication and Information Systems (CIS) Group will be supported by three NATO Signals Battalions located at Wesel, Germany, Grazzanise, Italy, and Bydgoszcz, Poland. These three will be complemented by various smaller elements (Deployable CIS modules) elsewhere.


    Naval Striking and Support Forces NATO (STRIKFORNATO), NATO Airborne Early Warning and Control Force (NAEW&CF) and Alliance Ground Surveillance (AGS) are part of the NATO Immediate Response Capability. They are multinational structures that are not part of the Command Structure, but are available for the Alliance and organized under Memorandums of Understanding and Technical Agreements (MOU/ TA) signed by the respective contributing countries.

    STRIKFORNATO is a rapidly deployable maritime headquarters that provides scalable command and control across the full spectrum of the Alliance’s fundamental security tasks. It focuses on maritime operations and, as part of NATO reforms, has moved from Italy to Portugal. It comprises 11 participating countries and serves as a link for integrating US maritime forces into NATO operations.

    Final agreement is awaited on the NATO NAEW&C Force. The Force Commander is conducting a comprehensive Force Review that will determine the size and shape of the Airborne Warning & Control System (AWACS) capability for the future and is adapting the capability to match the new manpower ceilings decided in the context of the new Command Structure. The NAEW&C Force comprises three elements: a multinational HQ (Mons) and two operational components, the multinational E-3A and the E-3D. NATO Air Base (NAB) Geilenkirchen, Germany, is home to 17 Boeing E-3A 'Sentry' AWACS aircrafts. NATO operates this fleet, which provides the Alliance with an immediately available airborne command and control (C2), air and maritime surveillance and battle-space management capability. The fleet of six Boeing E-3D aircraft based in Waddington, Lincolnshire, United Kingdom, is manned by RAF personnel only. The United Kingdom exercises limited participation, but her fleet of E-3D aircraft is an integral part of the NAEW&C Force.

    NATO is acquiring an Alliance Ground Surveillance (AGS) system that will provide SACEUR with the capabilities for near real-time, continuous information and situational awareness concerning friendly, neutral and opposing ground and surface entities. The AGS system will consist of five Global Hawk Unmanned Airborne Vehicles and the associated command and control base stations, as well as support facilities provided by the AGS’ main operating base at Sigonella, Italy. Using advanced radar sensors, these systems will continuously detect and track moving objects and will provide radar imagery of areas of interest and stationary objects. The system will be fully trained and equipped to participate in NATO approved operations worldwide and available at graduated levels of readiness. It is expected to be available to the Alliance in the 2015-2017 timeframe.

  • Evolution

    The Supreme Headquarters Allied Powers, Europe (SHAPE) was activated on 2 April 1951, in Rocquencourt, France, as part of an effort to establish an integrated and effective NATO military force. Allied Command, Atlantic, headed by Supreme Allied Commander Atlantic (SACLANT) was activated a year later, on 10 April 1952.

    In 1967, after France’s withdrawal from NATO’s integrated military structure, SHAPE was relocated to Mons, Belgium.

    The London Declaration of July 1990 was a decisive turning point in the history of the Alliance and led to the adoption of the new Alliance Strategic Concept in November 1991, reflecting a broader approach to security. This in turn led to NATO’s Long Term Study to examine the Integrated Military Structure and put forward proposals for change to the Alliance’s force structures, command structures and common infrastructure.

    In essence, the Cold War command structure was reduced from 78 headquarters to 20 with two overarching Strategic Commanders (SC), one for the Atlantic, and one for Europe; there were three Regional Commanders under the Supreme Allied Commander, Atlantic (SACLANT) and two under the Supreme Allied Commander, Europe (SACEUR).

    During the 2002 Prague Summit, NATO’s military Command Structure was again reorganised with a focus on becoming leaner and more efficient. The former Allied Command Europe (ACE) became the Allied Command Operations (ACO). The Supreme Allied Commander Europe and his staff at the Supreme Headquarters Allied Powers Europe (SHAPE) situated in Mons, Belgium, were henceforth responsible for all Alliance operations, including those previously undertaken by SACLANT. The reform resulted in a significant reduction in headquarters and Combined Air Operations Centres – from 32 command centres down to 9 – and reflected a fundamental shift in Alliance thinking.

    In 2010, the decision was taken to conduct a far-reaching reform of the NATO Command Structure as part of an overall reform of NATO. The reform was conducted with the development of the Strategic Concept 2010 firmly in mind and has focused on ensuring that the Alliance can confront the security challenges of the 21st century effectively and efficiently. The new Command Structure is forward-looking and flexible, as well as leaner and more affordable. In comparison to the previous structures, it will provide a real deployable, multinational, command and control capability at the operational level. It also offers a more coherent structure that will be understood by other international organisations and partners.

    The new Command Structure was approved by NATO defence ministers in June 2011. It transitioned to its new format (Transition Day) on 1 December 2012 and is expected to be fully implemented by the end of 2015.