By the early 20th century, Imperial Japan had established itself as the dominant force in Asia. Through ruthless military conquests, the small island nation greatly expanded its borders. The rising imperial power soon set its sights on conquering much of East Asia. By 1921, nearly a third of Japan’s national budget was dedicated to building one of the most powerful navies in the world. In response to Japan and other world powers rapidly expanding their naval strength, the Washington Naval Treaty was signed in 1922 to impose restrictions on the size and number of warships. However, American military planners were not convinced—rightfully so—that Imperial Japan would adhere to these new restrictions for very long. The United States, surrounded by two enormous oceans, seemed increasingly vulnerable.