United States Army, 7.12.1941

The Northeast, Central, Southern and Western Defense Commands were only paper organizations on 7 Dec 1941. They did not become operational until after Pearl Harbor. Slightly confusingly, they were commanded by the same generals as the First, Second, Third, and Fourth Armies, respectively – although the areas these commands encompassed were not identical.

The US government in the Pacific was divided between three different departments.
The Territories of Alaska and Hawaii were under the supervision of Territorial Governors who reported to the US Department of the Interior.
The Commonwealth of the Philippines was a protectorate, but both the President of the Philippines and the US High Commissioner reported to the Department of the Interior. These officials controlled the non-federalized militia and most emergency services.
The Panama Canal Zone was still under the administration of the War Department.

While the garrisons themselves in the Philippines, Hawaii, and Panama reported directly to the War Department in Washington DC, that in Alaska reported to the Fourth Army at the Presidio in San Francisco.

The designation "Department" was a holdover from the names given to military commands back before World War I. In 1920 all "departments" in the continental U. S. were redeignated "Corps Areas", but the Hawaiian, Panama Canal and Philippine Departments kept their names. In 1939, the Puerto Rican Department was added. In May 1941, the Panama Canal and Puerto Rican Departments were combined to form the Caribbean Defence Command, but the Army still referred to them as Departments. In July 1941, when MacArthur was recalled to duty, he called his command the "U.S. Army Forces in the Far East", but the Philippine Department still existed as a Service Command for USAFFE. In May 1941, the Corps Areas were redesignated as Corps Area Service Commands,