Japan launched an attack on Batan Island on 8 December 1941, to get control of the airbase on the island. Japan used this airbase to launch attacks on other islands. After taking most of the islands with little to no resistance, Japan was getting a very good position on the Philippines. On January 4, 1945, Bacnotan was liberated in the municipal town by combined American and Philippine Commonwealth troops and the local military units of the 121st Infantry Regiment, Philippine Commonwealth Army, USAFIP-NL are captured Baroro Bridge from the defeating Japanese Imperial forces.
The Japanese had launched an invasion of the Philippines on 8 December 1941, and, until Bacnotan, received no organized resistance. There, they reached troops with the 11th Infantry Division, Philippine Commonwealth Army, USAFFE. By flanking movement to the east, the Japanese were able to continue advancing with little difficulty. It was done around the same time as the Japanese Invasion of Legaspi.