Allied Command Operations (ACO)

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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.

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.
These figures cover Allied Command Operations and Allied Command Transformation.
The military command structure
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.

Source: NATO


L. J. De Rothschild

Senior Editor

NATO Section


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Robert Williams

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