[1] The Japanese had been officially planning a strike on the American fleet at their main base at Pearl Harbor in the Territory of Hawaii since early 1941, but the idea had been informally speculated for many years.

Early in 1941, President Franklin D. Roosevelt ordered a military buildup in the Philippines in the hope of discouraging further Japanese aggression in the Far East.

[citation needed] Batan Island was the first part of the Japanese invasion of the Philippines and occurred simultaneously with the attack on Pearl Harbor.

[1] However, over the next few days, the success of the Japanese bombing attack on Clark Field rendered the base at Basco redundant, and work was discontinued.

The landing again proceeded without incident, and possession of the small airstrip on Camiguin gave the Japanese a forward airbase only 35 miles from Aparri.

[1] Vice Admiral Sueto Hirose, the orchestrator of the invasion, was later found in Japanese-occupied West Sumatra and surrendered to Allied forces on 10 October 1945.