Holding out longer than any other Allied garrison attacked on December 7, 1941, the Philippines were an important target for the Imperial Japanese High Command. Navy and Army bombers from Formosa attacked in the late morning, and achieved the same success their comrades were enjoying over Pearl Harbor.
The war warning of December 6 had put US Army General Douglas MacArthur into action. When Pearl was being bombed, his planes were in the air, his shore defense were manned, and he thought the first attack would come his way, as the war plans expected. Unfortunately for MacArthur and the War Department, the Japanese had written their own war plans that called for the attack on the Philippines in late morning. The Americans and Filipinos were stunned when the attack came as the planes were on the ground and refueling. Most of the US Army Air Corps was destroyed on the ground. Bombers hit Cavite Navy Yard very hard, and the bleeding of the US Asiatic Fleet began.
MacArthur had spent twelve years in the Philippines, and had recently returned to the US Army after commanding the Filipino Armies wearing an elaborate gold braided uniform. He failed to provide the needed training, but was also hampered by a corrupt Filipino government and little assistance from the United States.
His army in December 1941 was made up of many different units that were not coordinated or had trained together on any useful basis. He had a huge force of almost 130,000 men, but the majority were Filipino units, only one of which was considered combat-ready. MacArthur planned for the expected Japanese attack using standard military doctrine for defense of the Philippines: retreat into prepared fortifications on Bataan peninsula and Corregidor, expecting a landing in Manila Bay.