Why did the Japanese attack Pearl Harbor?

Imperial Japan had sought to create a Greater East Asia Co-Prosperity Sphere through military expansion in Southeast Asia.

This was seen as a necessary step to reduce the overpopulation of Japan, and also provide resources such as rubber and oil which were in short supply due to economic sanctions imposed on Japan by the United States.

However, the aggressive nature of Japanese expansion during the 1930s, especially its brutal actions during the Second Sino-Japanese war led to America enforcing a trade embargo on Japan in 1941.

This cut off the crucial resources that Japan needed to continue its war efforts, and so the decision was made by the Japanese high command to launch a surprise attack on Pearl Harbor which would cripple America's ability to interfere in the region and provide access to vital resources once more.

The attack on Pearl Harbor was the result of a long-standing plan by the Japanese military to neutralize the American Pacific Fleet.

The architect of this plan was Admiral Isoroku Yamamoto, who believed that a direct strike on the fleet would cripple their ability to interfere with Japan's plans for expansion.

Yamamoto also feared that if the US were to occupy Japan's conquered territories, the United States would be able to use them as bases for a blockade on Japanese shipping routes.

Yamamoto believed that this would result in starvation for his people and ultimately lead to their defeat by the Allies.

Pearl Harbor was an important location for America because it was the main base of the US Pacific Fleet, which protected American interests and allies in Asia and the Pacific. 

Among the nineteen US navy ships that were at Pearl Harbor at the time of the attack, eight were battleships: USS Arizona, USS California, USS Maryland, USS Nevada, USS Oklahoma, USS Pennsylvania, USS Tennessee, and USS West Virginia. 

There were also three aircraft carriers stationed at Pearl Harbor: the USS Enterprise, USS Lexington, and the USS Saratoga. 

Yamamoto's plan involved sending successive waves of aircraft from the Japanese aircraft carriers to bomb as many American ships and aircraft as possible. 

The attack itself was carried out by six aircraft carriers and 353 planes launched from four separate air groups.

The first wave of planes targeted the American airfields and military installations on Oahu, while the second wave attacked the Pacific Fleet anchored in Pearl Harbor. 

The first wave of planes was led by Commander Mitsuo Fuchida, who had been trained in the United States and was familiar with the layout of Pearl Harbor.

The surprise attack caught the Americans completely off-guard when the first shots were fired at 7:55 am local time on Sunday, December 7th, 1941.

By 9:00 am all planes had returned safely to their carriers with only 29 being lost during the attack itself.

The American Pacific Fleet suffered significant damage. Specifically, the USS Arizona was sunk, killing over 1200 sailors and marines.

The battleships West Virginia, Oklahoma, California, and Tennessee were damaged or destroyed as well as many other smaller ships docked at Pearl Harbor.

More than 180 U.S. aircraft were destroyed and another 159 were damaged. Only 6 U.S. planes managed to get into the air to fight back. 

In total, the Japanese attack resulted in over 2400 casualties including civilians killed during strafing runs on Oahu by Japanese aircraft.

However, the attack on Pearl Harbor did not destroy any of the American aircraft carriers.

This was because none of them were in the harbor at the time of the attack. They were all on missions elsewhere in the Pacific Ocean.

This was a lucky coincidence, not a deliberate strategy by the US commanders, since the aircraft carriers would prove to be crucial in the subsequent war against Japan.

The attack on Pearl Harbor had a tremendous impact on both Japan and the United States.

Yamamoto's plan resulted in an immediate American declaration of war against Japan, which forced them to fight a two-front war with China and Russia as well.

The attack on Pearl Harbor was met with outrage by the American people and government. On December 8th, President Franklin D. Roosevelt addressed a joint session of Congress to declare war on Japan.

In his speech, Roosevelt referred to the attack as "a date which will live in infamy" and vowed that the United States would seek "vengeance in full measure."

One of the most important factors in the attack was the realisation that the American aircraft carriers at Pearl Harbor were not present at the time of Yamamoto's raid.

Yamamoto made a serious error in failing to anticipate that the aircraft carriers would be absent from port on their way back from delivering fighters to Wake Island and Midway Atoll.

Yamamoto had hoped for an unopposed attack, but despite this intelligence failure, his plan did achieve severe damage to the fleet. 

Despite suffering extensive damage, the Pacific Fleet was able to recover quickly.

Yamamoto did not anticipate the United States' ability to rapidly repair and replace damaged ships using their industrial might, which ultimately led to his defeat at the Battle of Midway six months later.

Yamamoto's failure in this regard has been attributed largely due to a poor understanding of American culture as well as his own arrogance.

Yamamoto's plan ultimately backfired and led directly to Japan's defeat.