The Planning of Pearl Harbor

On this date in 1941, the Imperial Japanese Navy launched an incredibly daring, technically sophisticated combined naval-aerial surprise attack on the U.S. naval base at Pearl Harbor, just northwest of Honolulu on the Hawaiian island of Oahu. The devastating aerial attack carried out by Japanese fighters, dive-bombers and torpedo planes crippled the U.S. Pacific fleet as a preamble to Imperial Japan’s lunge for strategic territories spanning the Pacific Ocean – but it also stirred the wrath of the American people, decisively ending U.S. isolationism and bringing the world’s largest industrial power squarely into the war against Japan and its European allies in Nazi Germany and Fascist Italy.

The Economic Vise

Pearl Harbor was born of strategic desperation. Over the previous couple years, Japan and the U.S. had been engaged in a tit-for-tat diplomatic and economic struggle, as the Roosevelt administration tried to restrain escalating Japanese aggression with embargoes on raw materials crucial for the Japanese war machine. Japan was heavily dependent on American supplies of oil and metal, with American shipments accounting for 80% of Japan’s oil and copper imports and almost half of its scrap iron imports.

Over several years the U.S. tightened the economic vise, responding to Japanese aggression in China and Southeast Asia by cutting off supplies of aircraft materials in 1939, scrap steel in 1940, and machine tools and metal ore in 1941. The final blow came with the suspension of oil deliveries in summer 1941.

At first, the Japanese hoped to negotiate their way out of the American economic embargo, but the Americans’ unwavering opposition to Japanese foreign policy convinced the Japanese leadership that further negotiation would be fruitless. They decided instead to deliver a knockout blow to the U.S. Pacific fleet with a surprise attack on Pearl Harbor, which would, they calculated, give Japan two years of unchallenged supremacy in the Pacific and a window in which they could conquer the oil-rich Dutch East Indies (today Indonesia) and the rubber plantations of Malaya. This, in turn, would give Japan enough resources to fight on once the U.S. rebuilt its Pacific fleet.

The odds were steep, to say the least. The plan required bringing a huge aircraft carrier battle fleet – comprised of six carriers, two battleships, and 48 combat and support vessels including cruisers, destroyers, submarines and tankers – 4,000 miles from the northeast coast of Japan to Pacific waters north of Hawaii in complete radio silence, a feat akin to smuggling an elephant through airport security. Ships in the attack fleet couldn’t communicate with home base, meaning there was no way to call off the attack without exposing their position.

Uphill Battle

In fact, the man in charge of planning the attack – the brilliant admiral Isoroku Yamamato, who had studied in the U.S. and respected American fighting spirit – advised against it, noting that even if it succeeded, Japan would still face an implacable enemy drawing on huge resources. He famously warned:

“Should hostilities once break out between Japan and the United States, it would not be enough that we take Guam and the Philippines, nor even Hawaii and San Francisco. To make victory certain, we would have to march into Washington and dictate the terms of peace in the White House. I wonder if our politicians (who speak so lightly of a Japanese-American war) have confidence as to the final outcome and are prepared to make the necessary sacrifices.”

But the hyper-nationalists in charge of Japan could not imagine submitting to what they perceived as American bullying, and decided on war, no matter how desperate, and no matter how steep the price. The die was cast.

After leaving Japan on November 26, the Japanese fleet steamed east across the Pacific, reaching a point about a thousand miles north of Hawaii on December 3. During their silent run, the Japanese ships were scattered by a sudden Pacific storm that lasted two days, stringing them out over hundreds miles of open water – but still managed to regroup with minimal use of short-range, low-power radio to communicate their positions, a remarkable feat of seamanship and navigation. Then from December 4-6, the fleet headed south until it reached a staging point a few hundred miles north of Oahu in the early morning hours of December 7.

Here the attack shifted from its naval phase to the aerial phase, with two waves of dive-bombers, fighters, and torpedo planes taking off from the carriers beginning at 6:10 a.m. Hawaii time. The first bombs fell at 7:48 a.m. Surprise was complete, as the operators of the primitive American radar mistook the approaching Japanese planes for a returning flight of U.S. B-17s.

Assisted by some ineffectual midget submarines, over two hours and 20 minutes 354 Japanese planes sank four American battleships, damaged three more and caused the last to run aground, while damaging or destroying ten other ships and over three hundred aircraft. The human toll came to 2,402 killed and 1,247 wounded, including 1,177 dead aboard the U.S.S. Arizona, the hardest-hit. Japanese losses were light, reflecting their success in achieving total surprise. Meanwhile Japanese forces fanned out across the Pacific, with near-simultaneous attacks on American forces in the Philippines and Guam, and tiny colonial garrisons in the Dutch East Indies and Malaya.

Although the attack was devastatingly successful, it was not the knockout blow Japanese planners had intended. Most importantly, the U.S. Navy’s Pacific carrier fleet was left untouched, since all three aircraft carriers were at sea during the attack. These would provide a crucial counterbalance to Japanese naval power in the Pacific in 1942, beginning with the stunning American victory at the battle of Midway.

Worse, the Japanese leadership badly miscalculated in their long-term strategy. In particular, they were over-optimistic about their ability to secure the long maritime supply lines from the oil wells of the East Indies to Japan; these proved vulnerable to American submarines, which helped strangle the Japanese economy in the final years of the war.

Last but not least, the effect on American morale was essentially the opposite of what the Japanese hoped. In the weeks following Pearl Harbor (which included Adolf Hitler’s declaration of war on the U.S. on December 11), approximately one million American men volunteered for military duty. This would be followed by a draft that eventually built the American military into 12-million-strong juggernaut by 1944, compared with Japan’s 4.3 million men in military service by the end of the war.

This post originally appeared in 2011.