I muri i te whakaekenga o Hapani ki Pearl Harbor me te urunga mai o te United States ki te Pakanga Tuarua o te Ao, i whakahoutia a Foster ki te mahi kaha me te taumata o te Kaihauturu i te Naval Reserve, a, i tukuna e te Perehitini a Franklin D. Roosevelt ki te whakahaere i nga tirotiro moana motuhake. Ko tētahi o ana mahi tuatahi, ko te whakahaere rangahau i te Rohe Canal o Panama
whai muri i te raupapa amuamu mai i te Lieutenant General o te ope taua a Daniel Van Voorhis, Kaiwhakahaere o te Caribbean Defense Command mo te mahi tahi a te Army-Navy.