The attacks were a tactical coup of Japan. . . . Despite their tactical successes, the attacks were a strategic disaster for both Japan and the Axis Powers generally. As a result of these attacks, the U.S., Britain, Australia and other Allies to formally declare war on Japan. . . . The Japanese high command's key mistake that prompted the attack was is mistaken belief that it was certain that any attack on the British Southeast Asian colonies, an attack crucial to its war plan, would bring the U.S. into the war. Since it thought U.S. entry into the war was inevitable, it sought to crush U.S. forces in the Pacific.
In fact, had Japan refrained from attacking U.S. possessions like Hawaii (not yet a state) and the Philippines, it might have postponed U.S. military involvement in the World War II significantly and might even have prevented U.S. intervention in the Pacific entirely.
[In the account of] Admiral James O. Richardson, commander of the Pacific Fleet . . . "At least as early as October 8, 1940, President Roosevelt believed ... 'that if the Japanese attacked Thailand, or the Kra Peninsula, or the Dutch East Indies we would not enter the war, that if they even attacked the Philippines he doubted whether we would enter the war[.]"
U.S. involvement in World War II, of course, was a central factor in the defeat of the Axis Powers, both Japan and Germany, less than four years later, with Japan enduring the destruction of Hiroshima and Nagasaki by nuclear bombs and surrending to the United States[.]The outcome of international military conflicts, more often than not, hinges more upon who else in the international community joins the parties as allies than upon the bravery of individual soldiers or the weapons available to the combatants.