Allied Command Operations, NATO's headquarters for all military plans and operations, is the successor to two historic strategic commands for NATO – Allied Command Europe and Allied Command Atlantic. Two years after NATO was founded in 1949, the members of the Alliance realized that a military command structure was necessary to ensure greater integration of NATO forces and proper lines of command in the event of a crisis or war. As a result, in 1951 the first strategic command, Allied Command Europe (ACE), came into existence under the command of General Dwight D. Eisenhower, US Army, who had the title of Supreme Allied Commander Europe or SACEUR. His headquarters – the Supreme Headquarters Allied Powers Europe or SHAPE – was located in the Parisian suburb of Rocquencourt, France. One year later the second major strategic command for NATO was activated. Allied Command Atlantic (ACLANT) had its headquarters in Norfolk, Virginia, USA, and was commanded by the Supreme Allied Commander Atlantic or SACLANT. The first SACLANT was Admiral Lynde D. McCormick, US Navy.
In 1967 SHAPE moved from Rocquencourt, France, to Casteau, Belgium, as a result of French President Charles de Gaulle's decision to withdraw his country from NATO's integrated military command structure. Headquarters ACLANT remained in its original location throughout its history.
At the Prague Summit in 2002 the member nations of NATO agreed on a major reorganisation of the NATO command structure under which there would only be one strategic-level command in charge of all NATO operations, with the title of Allied Command Operations (ACO), while a second strategic- level headquarters – Allied Command Transformation (ACT) – would be established to promote and oversee the continuing transformation of Alliance forces and capabilities through training and the development of new concepts and doctrine. The headquarters for ACO and ACT were located in the sites of the two previous strategic commands, ACE and ACLANT, thus in Casteau, Belgium and Norfolk, Virginia. For both historical and financial/legal reasons, the headquarters of ACO retained its traditional title of SHAPE and its commander the traditional designation as SACEUR. In essence, when the new organisational structure became in effective in 2004, SHAPE simply added to its existing responsibilities in Europe the ocean areas previously under ACLANT. At the same time some of SHAPE's transformational activities moved over to the new Allied Command Transformation, whose commander is known as the Supreme Allied Commander Transformation or SACT.