The central reason for the Japanese invasion of the archipelago was geography. One of the central motivations for both the IJA and IJN planners to join the war was to seize what they termed the "Southern Resources Area," which encompassed modern-day Borneo, Indonesia, and the countries of SE Asia. Japanese planners believed that natural resources from this region would allow Japanese industry in the Home Islands and, to a lesser extent, Manchuria and Korea, to be run on an autarkic basis. The Philippines ran athwart the sea lanes that the Japanese would use to bring the raw materials from the Southern Resources Area back to the Japanese industrial core; so leaving the Philippines unmolested would negate any strategic advantage Japan would accrue from occupying the Southern Resources Area as the US, which held the Philippines as a protectorate, could interdict Japanese convoys carrying raw materials back to Japan. Moreover, the IJN's central strategy of annihilating the Pacific Fleet in a decisive battle was dependent upon the USN drive through the Central Pacific. Invading and occupying US bases in the Philippines would allegedly act as a lure for the USN to run the gauntlet of Japanese naval bases in Micronesia, instead of operating directly against the Home Islands, and allow the numerically smaller IJN fleet to concentrate and defeat the USN in a latter-day Tsushima.