During the Second World War, with air raids by Japanese fighters and bombers, the province of Cagayan suffered much destruction by bombing and later invasion. Japanese Imperial forces entered Cagayan in 1942. While under the Japanese Occupation, several pre-war infantry divisions and regular units of the Philippine Commonwealth Army were re-established during the period on January 3, 1942 to June 30, 1946. They established general headquarters, camps and garrisoned troops in the province of Cagayan, and began operations against the Japanese Occupation forces in the Cagayan Valley. This included sending troops to the provinces of Cagayan and Isabela, and helping the local soldiers of the 11th and 14th Infantry Regiment of the USAFIP-NL, the local guerrilla fighters and the U.S. liberation forces. They fought against the Japanese Imperial forces from 1942 to 1945.