What was the only part of the current United States invaded by the Japanese during WWII?

During World War II, the only part of what is now the United States to be invaded by Japanese forces was the remote Aleutian Islands of Alaska. In June 1942, six months after the attack on Pearl Harbor, Japanese troops landed on and occupied the islands of Attu and Kiska, which were then part of the U.S. Territory of Alaska. This marked the first time since the War of 1812 that foreign troops had occupied American soil, causing significant concern among the American public.

The Japanese invasion of these far-flung islands served multiple strategic purposes. Many historians believe it was primarily a diversionary tactic, intended to draw the U.S. Pacific Fleet away from the pivotal Battle of Midway, which was launched simultaneously. Additionally, controlling the Aleutians was seen by Japan as a way to protect their northern flank and potentially prevent any future American attacks on the Japanese homeland (Review) from that direction. However, the harsh and unpredictable weather conditions, characterized by dense fogs, high winds, and rugged terrain, made the islands a challenging and isolated battleground for both sides.

American and Canadian forces ultimately launched a campaign to reclaim the islands. The battle to retake Attu in May 1943 was particularly fierce and costly, fought in brutal conditions. Subsequently, in August 1943, Allied forces landed on Kiska only to discover that the Japanese garrison had secretly evacuated. Though often overshadowed by other major campaigns of the war, the Aleutian Islands campaign was a critical effort to expel an occupying enemy from American territory and is sometimes referred to as the "Forgotten Battle."