During World War II, there were two areas which had supreme commanders in name and three others which effectively had supreme commanders. The two in name were the Supreme Allied Command South East Asia (SACSEA) and Supreme Commander Allied Expeditionary Force (SCAEF) in northwest Europe. The Allied Mediterranean theatre's Commander-in-Chief, Allied Force, the American Commander-in-Chief South West Pacific and Commander-in-Chief Pacific Ocean Areas also functioned as de facto supreme commanders. These commanders reported to the Combined Chiefs of Staff, although in the case of the American commanders in the Pacific and SACSEA, the relevant national command authorities of the Joint Chiefs of Staff or the Chiefs of Staff Committee had responsibility of the main conduct of the war in the theatre of operations.
General of the Army Dwight Eisenhower was the most high profile of the supreme commanders. He served successively as the Allied Mediterranean theatre's Commander in Chief, Allied Force and then as European theatre's Supreme Commander Allied Expeditionary Force (SCAEF). Eisenhower was succeeded as Commander in Chief, Allied Force by Field Marshal Henry Maitland Wilson who was in turn succeeded by Field Marshal Harold Alexander. The post of Supreme Commander South East Asia Command (SACSEA) was occupied throughout most of its existence by Admiral Lord Louis Mountbatten. The post of the American Commander-in-Chief South West Pacific was held by General of the Army Douglas MacArthur.
Following the end of the war, the term came into use again with the formation of NATO, at which point Eisenhower again found himself a Supreme Allied Commander.
The NATO structure is divided into two commands, one for operations and one for transformation. Each has a Supreme Allied Commander as highest ranking military officer.
Until June 2003, the operational structure of NATO was divided into "Europe" and "Atlantic". Correspondingly the commanders were known as Supreme Allied Commander Atlantic (SACLANT) and Supreme Allied Commander Europe (SACEUR).
The first SACEUR (1951-1952) was General Dwight Eisenhower. The current (since 2007) Commander is General Bantz J. Craddock (Army), who succeeded General James L. Jones (Marine Corps). The Supreme Commander is always an American, with a deputy officer from another NATO member. For a full list of officers appointed to the position of SACEUR, please see list
In June 2003, the SACLANT organisation was decommissioned and Allied Command Transformation was established. This is a transitory command, intended to reshape the NATO command structure to respond to rapidly changing world situations and technology. The commander of the organization is General James Mattis, U.S. Marine Corps. The headquarters of ACT is at the former SACLANT headquarters in Norfolk, Virginia, USA.