Japan did not intend to alert the Americans by prior declaration of war

Perhaps to ease the burden of Japan's war guilt, some accounts of the Japanese attack on Pearl Harbor have suggested that Japan intended to submit a formal declaration of war to the American Secretary of State, Mr Cordell Hull, immediately prior to the attack on Pearl Harbor, and that this formality was frustrated by decoding and clerical delays in the Japanese embassy. Such delays may have occurred, but the document submitted to Mr Hull on this occasion was not a formal declaration of war. It was a summary of Japanese grievances, coupled with a blunt announcement that Japan was terminating the lengthy diplomatic negotiations between Ambassador Nomura and Secretary of State, Cordell Hull. Japan formally declared war on the United States several hours after the last Japanese aircraft had returned to its carrier from the smoking ruins of the American battleship fleet at Pearl Harbor.

The carrier USS Enterprise was at sea when the Japanese struck Pearl Harbor. The failure of the Japanese to destroy the American aircraft carriers and their fuel supply at Pearl Harbor contributed significantly to the defeat of Japan.

The Japanese tactical victory was largely illusory

Admiral Yamamoto's huge gamble appeared to have paid off handsomely. The American Navy's Pacific battleship fleet had been crippled, and the Japanese were confident that they could pursue their plans to seize the Philippines, Malaya, British Borneo and the Dutch East Indies without fear of intervention by the United States Pacific Fleet.

While conceding the serious damage to the battleships and loss of life at Pearl Harbor, the Japanese tactical victory was largely illusory. The battleships were all old and slow, and three were back in action within one month. The outcome of the Pacific War would be largely determined by fast aircraft carriers rather than lumbering battleships. Fortunately for the United States and Australia, the powerful American aircraft carriers Lexington and Enterprise were at sea when the Japanese attack took place and escaped damage. The aircraft carrier Yorktown was on temporary duty in the Atlantic at this time, and was immediately ordered back to Pearl Harbor after the Japanese attack. The aircraft carrier Saratoga was at the San Diego naval base on the American West Coast when the attack occurred. The American heavy cruisers and submarines in Pearl Harbor were also undamaged.

If the vital fuel storage tanks had been destroyed in either attack, the surviving American warships, including the carriers Lexington and Enterprise would have been deprived of fuel to operate. The course of the Pacific War would have been dramatically altered in Japan's favour. Japanese submarines could have played havoc with tankers attempting to bring fresh fuel supplies from the United States across 2,200 miles (3,960 km) of open Pacific Ocean.

The ship repair and servicing installations at Pearl Harbor had not been Japanese priority targets and were quickly repaired. The aircraft carrier Yorktown received serious damage in the Battle of the Coral Sea in May 1942. If the vital ship repair facilities at Pearl Harbor had been destroyed, there is a real possibility that Yorktown would have been unable to participate in the pivotal Battle of Midway in June 1942. If Yorktown had been absent from Midway, it is likely that the course of the Pacific War would have been altered in Japan's favour.

The neglect to destroy these vital supply and servicing components of the Pacific Fleet would rebound on the Japanese during the first six months of 1942 when the American aircraft carriers Lexington and Enterprise, augmented by the arrival of the carriers Yorktown and Hornet from the Atlantic Ocean, would exact from the Japanese a heavy penalty for Pearl Harbor. Between 1942 and 1945, American submarines based at Pearl Harbor would play a key role in defeating Japan by strangling its supply lines to its vastly expanded western Pacific empire.

The heavy strategic cost of Pearl Harbor to Japan

The largely illusory tactical victory at Pearl Harbor was achieved at enormous strategic cost to Japan. In terms of power relationships in the Pacific region, the Pearl Harbor attack did not significantly weaken the operational effectiveness of the United States Pacific Fleet. The Japanese attack was viewed by many Americans as a cowardly stab in the back by a Japanese Imperial Navy that was afraid to meet a weaker US Navy openly in a fair contest of strength. The perceived treacherous nature of the attack in peacetime, the loss of American battleships, and the high death toll, galvanised and united American public opinion against Japan. It enabled President Roosevelt to mobilise America's wealth and industrial strength to defeat Japan as well as Germany. Despite his understanding of the United States and its people, Admiral Yamamoto failed to appreciate that it made no sense for Japan to make a fiercely determined enemy of such a powerful nation when there were no compelling reasons to do so.

As mentioned when dealing with Imperial Japan's Path to World War II, it is very unlikely that the United States Pacific Fleet would have challenged the Japanese Imperial Navy if Japanese aggression in South-East Asia had been limited to the British and Dutch colonies which possessed the oil, rubber, and other resources coveted by Japan . There are three important reasons for this.

During the 1930s, the United States entered a lengthy period of isolationism and neglected to maintain and modernise its navy. Many of the warships and naval aircraft of the United States Navy were obsolete in 1941. By contrast, Japan had the largest and most modern navy in the Pacific in 1941. America's attention and resources were primarily focussed on the war in Europe and the Atlantic Ocean. After the United States Navy had been split into Atlantic and Pacific Fleets in 1941, the American naval commander at Hawaii, Admiral Kimmel, was left with a fleet of old battleships, and only three aircraft carriers to pit against Japan's eleven aircraft carriers and the huge modern battleships Yamato and Musashi.

In addition to the operational weakness of the United States Pacific Fleet in 1941, there was an important policy factor that would have inhibited a direct confrontation with the Japanese Imperial Navy at that time. At the instigation of the British Prime Minister, Winston Churchill, the United States and Britain had agreed in early 1941 that, in the event of war between the United States and Japan, the Americans would adopt a defensive posture towards Japanese aggression in South-East Asia. This defensive policy was assigned the code reference "Rainbow 5", and it largely superseded the more aggressive "Plan Orange" which envisaged involvement of the United States Pacific Fleet in active defence of the Philippines against Japanese aggression. Rainbow 5 gave the highest priority to winning the war in Europe, and would have sacrificed Australia, British and Dutch colonies in South-East Asia, and even the Philippines, to the Japanese. Fortunately for Australia, the Japanese attack on Pearl Harbor and its impact on public opinion in the United States forced a drastic readjustment of its Pacific Ocean priorities by the American government.

The third reason relates to public feeling in the United States which was heavily isolationist and divided prior to the attack on Pearl Harbor. The attack angered Americans, and united them against Japan. It refocussed America's attention on the Pacific and brought Japan, without pressing need, into deadly conflict with a powerful adversary filled with determination to exact revenge for what it viewed as an act of treachery.

It is a sobering thought for Australians that, but for Pearl Harbor, their country would probably have been forcibly incorporated into Japan's Greater East Asia Co-Prosperity Sphere.

Review of 20th Century Fox Pearl Harbor attack film "Tora! Tora! Tora! (1970)