The 1925 Japanese invasion of the United States was a Pacific War military operation undertaken by Japanese Imperial forces in the spring and summer of 1925 in an attempt to force an early peace with the United States. With as many as 6,500,000 troops involved in the invasion, as well as over a thousand naval vessels and three thousand supporting aircraft, it was the largest single military operation in human history. Despite overwhelming numbers and early victories in California, the greater strategic goal of forcing an American capitulation was not achieved, and after the repulsion of Japanese forces in Oregon and the Colombian victory at Panama, the invasion of the United States was unsustainable and Japanese forces had withdrawn completely by the end of January 1926.
Early Advances and Victories
On March 2 of 1925, Japanese battleships bombarded the major cities of Los Angeles, San Diego, Tacoma, and San Francisco. The bombardments caused severe damage to Los Angeles and San Diego, while the bombardments of San Francisco and Seattle were, by and large, ended by American patrol boats, who torpedoed the battleships that fired upon the cities.
The first Japanese troops and aircraft were spotted at the beaches of Santa Monica, and quickly defeated the American garrison at the Battle of Hollywood. The Japanese soldiers continued to advance, defeating a second American garrison at the Battle of San Bernardino, and another at Temecula. At San Diego, the two sides clashed in a fourteen-week campaign that resulted in a decisive (strategic) victory for the Americans, though they were later forced to retreat when word of more Japanese soldiers en-route to the West Coast arrived. In Northern California, San Francisco and Tacoma were able to hold out until the end of the war, but Monterey, all of central Oregon and Olympia fell. The Americans later regrouped to push the Japanese out of Northern California, Oregon, and Washington, and then began a massive counterattack that effectively forced the Japanese off American soil.
While regarded as a strategic failure, the invasion is regarded as an impressive initial success, due to the relative maintenance of the Japanese supply lines across the Pacific Ocean throughout 1925, the subjugation of the American Naval presence in the Pacific through the seizure of or destruction of major American ports and naval bases, the interference with the crucial economic supply lines in the western United States, in particular California, and the sheer size of an invasion force establishing a foreign foothold so far away from home. The Japanese invasion of the United States was a crucial component of the North American front of the Pacific War.