 MacArthur became the Supreme Commander Southwest Pacific Area ( SWPA ) on 18 April 1942 , although he preferred to use the more conventional title of Commander in Chief . MacArthur 's first General Order created five subordinate commands : Allied Land Forces , Allied Air Forces , Allied Naval Forces , United States Army Forces in Australia ( USAFIA ) , and the United States Army Forces in the Philippines . The last command had a short life . Lieutenant General Jonathan Wainwright 's United States Army Forces in the Philippines disintegrated over the following three weeks , and disappeared entirely when Wainwright surrendered on Corregidor on 6 May . 
