On 7 December 1941, Japanese planes attacked the American naval base at Pearl Harbor.

Today, the small island nation’s decision to wage war on the mighty United States seems incredibly foolish.  But in 1941, it was not all that absurd.  The Japanese had spent the 1930s expanding into Southeast Asia and developing a military strong enough for the job.  The United States had spent the decade bogged down in economic depression and committed to avoiding the war brewing in Europe.  The Japanese had more men in uniform (2.4 versus 1.5 million) and more planes (7500 versus 1200).  The US Navy had more combat vessels, but  a large percentage of these were committed to the Atlantic. 

The Japanese also benefitted from pursuing comparatively local objectives.  They wanted to secure their own turf, their sphere of influence in their corner of the world. Should the United States choose to interfere, it would be taking on a conflict thousands of miles from its own shores.

It is worth considering how events might have played out had Japan just continued to flex its expansionist muscles in Asia.  One half of its military master plan called for just that—expand south from Japan and take Hong Kong and the Philippines, then increase their control over China and Indochina before attacking British Malay and Singapore. 

But the Japanese high command decided in late 1941 to preempt any outside interference.  To ensure that the United States did not meddle in Japan’s Asian activities, they would deliver a nerve shattering, psychologically and militarily paralyzing attack on Pearl Harbor. 

So in late November, six aircraft carriers packed with 411 planes set off for Pearl Harbor. The planes were armed with special armor-piercing heads designed to penetrate the decks of battle ships. They left from the Kurile Islands, north of Japan, correctly guessing that from there, they were less likely to be detected by American patrol planes.  

Their assumptions were correct; the carriers were not detected.  But still American military officials knew that something was cooking.  The Japanese code had been broken much earlier. Messages revealed that some sort of major military operation was impending.  They also knew that Japan’s ambassador in Washington had been instructed to deliver a note of some sort to the US State Department on 7 December.  But their best guess was that Japan was preparing to attack British Malay.  A few alarmists worried about the Panama Canal.  

No one seriously considered Pearl Harbor.  Even when radar operators in Hawaii picked up a wave of incoming aircraft, they concluded that what they detected were some anticipated new planes flying in a bit off course.  Military officials in Hawaii were not exactly complacent; they were afraid that Japanese-Hawaiian saboteurs might attack their grounded aircraft—so they stacked them in tight formation to make them easier to guard. 

The first attack hit Pearl at 7:55.  The second came at 8:15.  The rigorously trained pilots shelled their assigned ships with deadly accuracy; the American planes stored in tight formation were mowed down like dominoes.  By the time it all ended, four battle ships, three destroyers, and three light cruisers had been sunk and another four battle ships were damaged; 188 planes had been destroyed; and 2280 people had been killed.

Not everything went according to the Japanese plan.  The aircraft carriers that would prove so critical to the American war effort had all been recently moved out for one reason another.  The note that was to be delivered to the state department simultaneous to the attack took too long to decode and therefore was not delivered until a half hour after the attack.  Perhaps most important, while the attack did stun Americans, it did not paralyze them.  On 8 December, Congress approved, with only one dissenting vote, a declaration of war against Japan.