The participation of a Eurasian power, Soviet Russia, gave the Weir a new dimension. The American-Japanese war made it a world war. After the fall of France, the Vichy government was forced to give the Japanese free access to Indochina. This enabled Japan to isolate China by blocking the road and the railway to Yunnan. The German invasion of Soviet Russia had surprised the Japanese command, but the Japanese declined a German invitation to invade Siberia. Instead they meticulously prepared a campaign to conquer South East Asia. They could not realize the plan without first preventing a counter-attack by the American fleet. On 7 December 1941 a daring air raid caught the American fleet riding at anchor several thousand miles away in Pearl Harbour. It was completely successful. The American fleet, except for three aircraft carriers, was disabled for months afterwards. Two days later, Japanese planes sank two powerful battle ships of the Royal Navy. The Asian seas became the private domain of the Japanese air and sea forces, and were to remain so for some time. The United States had been caught by trickery. The previous controversy about American participation in the war was silenced and she entered the war with unhesitating resolution. Her industrial potential was immense, buta functioning war industry and a powerful army had still to be organized. The air force had scarcely been established and half the fighting fleet had been sunk. The Japanese campaign was quick and thorough. In a few months, Hong Kong, the Philippines, the atolls in the central Pacific, the Dutch East Indies, Malaya and Singapore fell to Japan one after another. A peaceful entry7 into Siam was followed by the capture of Burma, the invaders winning the confidence of local nationalists by endorsing their agitation against European colonialism. India and Australia were threatened and troops had to be recalled from the Middle East to defend them. The Pacific theatre of war covered an area incomparably greater than that of western Europe. Tokyo is over 4,000 miles from Hawaii, and Midway Island is 6,000 from Burma. The Japanese had to feed their troops and protect their convoys from American submarines, while consolidating their vast new empire and making it productive before the Americans could take the offensive. The Americans might then be discouraged from fighting back. It was not yet clear whether their naval forces, their air force, their merchant marine and their economy would be able to rise to the occasion. Japanese and German victories placed their enemies in a precarious position between June 1941 and the spring of 1942. America, being new to submarine warfare, lost a catastrophic tonnage of shipping to the Germans in the Atlantic. It seemed that Germany, Italy and Japan might succeed in carving up the world as they had planned in September 1940 in their Tripartite Pact.