Japan launched a surprise attack on the Philippines on December 8, 1941, just ten hours after the attack on Pearl Harbor. The defending Philippine and United States troops were under the command of General Douglas MacArthur, who was designated commander of the United States Armed Forces in the Asia-Pacific region. Under the pressure of superior numbers, the defending forces withdrew to the Bataan Peninsula and to the island of Corregidor at the entrance to Manila Bay. Manila, declared an open city to prevent its destruction, was occupied by the Japanese on January 2, 1942. The Philippine defense continued until the final surrender of United States-Philippine forces on the Bataan Peninsula in April 1942 and on Corregidor in May.

The Japanese military authorities immediately began organizing a new government structure in the Philippines. Although the Japanese had promised independence for the islands after occupation, they initially organized a Council of State through which they directed civil affairs until October 1943, when they declared the Philippines an independent republic. (Second Philippine Republic). Japanese first dissolved the Commonwealth of the Philippines and established the Philippine Executive Commission, a caretaker government. All political parties were banned and replaced by the non-partisan KALIBAPI –Organization in the Service of the New Philippines.

A constitution was formed by the Preparatory Commission for Independence. The Preparatory Commission, led by Jose P. Laurel, presented its draft Constitution on September 4, 1943 and three days later, the KALIBAPI general assembly ratified the draft Constitution. By September 20, 1943, the KALIBAPI's representative groups in the country's provinces and cities elected from among themselves fifty-four members of the Philippine National Assembly which elected Jose P. Laurel as President of the Republic of the Philippines. Most of the Philippine elite, with a few notable exceptions, served under the Japanese.

Japanese occupation of the Philippines was opposed by increasingly effective underground and guerrilla activity that ultimately reached large-scale proportions. Their effectiveness was such that by the end of the war, Japan controlled only twelve of the forty-eight provinces. Occupation ended with Japan's formal surrender on September 2, 1945.

 

Miniature Sheet number 1: Proclamation of independence, issued on October 14, 1943:

 

Miniature Sheet number 2: National Heroes (depicting Dr. Jose Rizal, Apolinario Mobini and Fr. Jose Burgos), issued on February 9, 1944: