The Pacific Theater of Operations is the area of operations of U.S. forces during the Pacific War of 1941-45. A theater of operations is a land or sea area, and the airspace above it, established to employ one's forces to neutralize a strategic threat to national or alliance/coalition interests in regional or general conflict; it is part of the theater (of war); normally the nation's highest leadership and the respective theater (of war) commander would designate a part of the theater as the theater of operations in case of a major regional or national emergency and general war; the theater of operations can also be established in the case of a major counterinsurgency effort. From mid-1942 until the end of the war in 1945, there were two U.S. operational commands in the Pacific: Pacific Ocean Areas (POA; divided into Central Pacific Area, North Pacific Area and South Pacific Area), commanded by Admiral Chester Nimitz, Commander-in-Chief Pacific Ocean Areas South West Pacific Area (SWPA), commanded by General Douglas MacArthur, Supreme Allied Commander South West Pacific Area. In addition, during 1945, General Carl Spaatz commanded the separate U.S. Strategic Air Forces in the Pacific. Because of the complementary roles of the United States Army and the United States Navy in conducting war in the Pacific theater, there was no single Allied or U.S. commander (comparable to Eisenhower in the European Theater of Operations) in the Pacific. Indeed, the organizational structure was rather complex, requiring the frequent involvement of the Joint Chiefs of Staff and the Army and Navy commanders each reporting to both the Secretary of War and the Secretary of the Navy. The Japanese Combined Fleet was led by Admiral Isoroku Yamamoto, until he was killed in an attack by U.S. fighter planes in April 1943. Yamamoto was succeeded by Admiral Mineichi Koga (1943–44) and Admiral Soemu Toyoda (1944–45)..