Naval Base Melbourne became the South West Pacific Area Command Headquarters after the 1941 invasion of the Philippines.

General Douglas MacArthur, after escaping the Philippines, set up his Headquarters after his arrival on 21 March 1942.

MacArthur was appointed Supreme Commander of all Allied Forces in the South West Pacific Area.

The US Navy also set up a Headquarters a Melbourne, Allied Naval Forces Southwest Pacific Area under Commander Vice Admiral Herbert F.

[1] MacArthur and Leary used the empty Trustees Executive building at 401 Collins Street, Melbourne for headquarters.

[2][3][4] With the loss of Naval Base Manila in 1941, the US Navy and United States Army need a safe South West Pacific port to stage a reply to Empire of Japan advances.

The existing port facilities at Melbourne were large enough to support the staging of future action.

The Melbourne Cricket Ground was used to house the staging of American and Australian troops, called Camp Murphy.

The depot worked with the Townsville Naval Section Base, which had an Anti-aircraft Ordnance Training Center.

Marines trained on field exercises live overhead firing, machine gun use, and mortar use.

With the fall of the Philippines the center was moved to Naval Base Manila's Corregidor Island.

US Navy Cryptologists and other Naval intelligence personnel were taken off Corregidor Island by submarines on 8 April 1942 after the fall of Manila.

To be low key the unit was based in the Monterey Apts on Arthur Street and the Moorabbin Town Hall.

It was run under the United States Seventh Fleet for the Naval Intelligence Center and opened in March 1943.