80 years after Pearl Harbor, here's how the attack changed history

Certain of inevitable war with the U.S., Japan launched a preemptive strike that shocked Americans and prompted the nation to enter World War II.

Masao Asada had just finished delivering groceries around Pearl Harbor, Oahu, when he heard some huge booms. No big deal, he thought—he was used to hearing noise from dredging activity in the Pacific Ocean lagoon. But the booms kept coming.

Asada jumped in his truck and drove toward the pier used by the U.S. Navy and Army. En route, he was flagged down by the driver of another car. “Get out of here!” the man shouted, Asada recalled in an oral history taken years later. “This is not practice! It’s war.” That’s when Asada looked to the sky and saw Japanese warplanes zooming overhead.

The grocery store owner was one of the thousands of eyewitnesses to Japan’s surprise attack on Pearl Harbor on December 7, 1941—an act of war that, though just 90 minutes long, irrevocably changed the course of world history. 

(Pearl Harbor survivors forgive—but can't forget.)

The lead-up to the Pearl Harbor attack

Tensions between Japan and the U.S. simmered throughout the early 20th century and came to a boil in the 1930s as Japan attempted to conquer China, even attacking civilians. In 1937, China and Japan went to war. By 1940, the U.S considered the Japanese expansion into China threatening enough to its interests that it began to provide military aid to China and started to sanction Japan. After Japan signed mutual defense pacts with Nazi Germany, Italy, and the Soviet Union in 1940 and 1941, the U.S. froze Japanese assets and forbade all exports into Japan.

Meanwhile, Nazi Germany continued its conquest of much of Europe. Though the U.S. was officially neutral in both conflicts, its stance was increasingly challenged both by Japan and Nazi Germany’s wars.

Neutrality was the most divisive public issue of its day, and a majority of the American public, which remembered the losses of World War I and was still recovering from the effects of the Great Depression, opposed entering any war overseas. Still, many Americans wanted the nation to help its embattled allies. President Franklin D. Roosevelt accomplished this through the Lend-Lease Program, which provided allies like Great Britain and China with weapons and military equipment.

But as Japan continued its war with China, a conflict with the U.S. became all but inevitable, prompting Japanese leaders to assess their options. The U.S. Navy was formidable, and Japan didn’t have the resources it needed to eliminate the American threat to their imperial ambitions. But they had one trick up their sleeve: surprise. Admiral Yamamoto Isoroku convinced Japan’s military officials that instead of declaring war on the U.S., they should confront them in the Pacific, doing as much damage to the Pacific Fleet as possible.

Planning the attack

While mainland U.S. forces mobilized in the wake of a surprise attack, Yamamoto argued, Japan could seize strategic Pacific islands. Japan was desperate for supplies, and the islands that lay between Japan and the furthest U.S. territory in Hawaii could provide much-needed oil and rubber.

Yamamoto spent months patiently planning the operation with naval captain Minoru Genda and others. In December 1941, Japan’s monarch, Hirohito, finally bowed to months of pressure from the military and authorized war. 

(Rare World War II maps reveal Japan's Pearl Harbor strategy.)

Despite evidence that Japan was building up air forces, the attack took the U.S. by surprise. On December 6, 1941, Army intelligence officers even intercepted a message that indicated war was imminent. But the military had no idea Pearl Harbor was the target—and by the time the message was en route to a telegraph office in Honolulu, the attack had already begun.

What happened December 7

The first shot of the attack on Pearl Harbor was actually fired before dawn by the U.S.S. Ward, an American destroyer that had been alerted to an early-morning submarine periscope sighting near the harbor entrance. The Ward sank the submarine. But since American forces did not expect an aerial assault, there was no general alarm. At 7:48 a.m. Hawaiian time, the first wave of Japanese dive bombers began flying over Pearl Harbor. Their targets were Navy-held Ford Island and seven nearby battleships located along what was known as “Battleship Row.”

Within minutes, much of the U.S. fleet had been damaged or destroyed. Over the course of two waves, a total of 353 Japanese planes and 28 submarines irreparably destroyed two battleships, Oklahoma and Arizona, and damaged all of the rest and several other fleet craft. The Japanese also targeted nearby airfields.

Though caught by surprise, the Americans did fight back. They manned antiaircraft guns and even got some airplanes off the ground; in all, 29 Japanese planes were shot down during the attack.

The toll of Pearl Harbor

Ultimately, nearly 2,400 Americans died. Nearly half of those deaths took place on the Arizona, which took a direct hit to its hull. Thirty-eight sets of brothers, including multiple sets of three brothers, served on the ship, and only one of those sets survived.

Some civilians were killed by friendly fire when anti-aircraft ammunition that did not detonate while being fired at Japanese aircraft fell. Only 64 Japanese servicemen were killed that day.

The U.S. enters World War II

The attack shocked the nation—and thrust the U.S. into a war it had managed to sidestep for years. The day after the attack, President Roosevelt asked Congress for a declaration of war against Japan. Calling December 7 a “date which shall live in infamy,” he told the U.S. Congress that the nation was in grave danger. Only one member of Congress, Representative Jeannette Rankin of Montana, voted against the declaration. Rankin, a pacifist and the first woman in Congress, had also voted against the U.S. entering into World War I.

On December 11, both Germany and Italy honored their pact with Japan and declared war against the U.S., which swiftly reciprocated. What followed would be a conflict that laid waste to much of Europe and Japan and that ended in 15 million battle deaths, 25 million wounded in battle, and at least 45 million civilian deaths. Ultimately, 416,800 American service members would die in the war.

Pearl Harbor had other brutal legacies. The Japanese military’s act was used to justify the internment of about 120,000 people of Japanese descent in the mainland U.S., including 70,000 U.S. citizens. And it forever ended the U.S.’ pre-1941 stance of isolationism and neutrality.

The attack on Pearl Harbor marked the entry of the world’s mightiest military power into World War II. It was also a turning point for the nation. “Everyone I talk to seems to feel that the old world we lived in before December 7, 1941 has passed out of existence,” Pittsburgh cab company executive Paul L. Houston said in a man-on-the-street interview in February 1942. “And we are in a whole new universe.”

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