The Japanese attack on Pearl Harbor stunned the world – and brought the USA into the Second World War. The attack was made without warning and without a declaration of war, a fact which ensured a devastating Japanese victory but meant also that the USA would fight hard to achieve revenge.
Following the defeat of France by Germany, the Japanese had insisted that they be allowed to station troops in French colonies in Indo-China. Under pressure from Germany, France had agreed. Although there was no formal alliance between Italy, Germany and Japan they became know collectively as the Axis Powers. US President Roosevelt viewed the move with deep suspicion. He was already opposed to the Japanese invasion of China and feared that this presaged a greater expansion still. He introduced an immediate trade embargo, along with the British, and persuaded the Dutch government-in-exile in Britain to suspend exports of oil from the East Indies to Japan.
Without oil from the East Indies and rubber from British Malaya the Japanese army would quickly grind to a halt. The Japanese decided to invade both territories to secure the supplies, but worried about the US reaction. If the US declared war, the Japanese would be severely overstretched, particularly at sea. The only way to avoid overstretch was to destroy the US Pacific Fleet at the outbreak of war. Thus it was decided to assault the main US naval base at Pearl Harbor without warning.
Planned by Admiral Yamamoto, the attack was to be made by aircraft launched from aircraft carriers. A convenient storm front was used to mask the approach of the Japanese fleet from the American base until the moment that the aircraft were flown off just after dawn on 7 December. Among the 350 Japanese aircraft were conventional fighters and bombers, plus torpedo bombers equipped with specially designed torpedoes that would run just below the surface in the shallow waters of Pearl Harbor.