In the northern-hemisphere summer of 1940 Germany rapidly defeated the French Third Republic, and colonial administration of French Indochina (modern-day Vietnam, Laos and Cambodia) passed to the French State (Vichy France). In September 1940 Japanese troops first entered parts of Indochina; and in July 1941 Japan extended its control over the whole of French Indochina. The United States, concerned by Japanese expansion, started putting embargoes on exports of steel and oil to Japan from July 1940. The desire to escape these embargoes and to become self-sufficient in resources ultimately contributed to Japan's decision to attack on December 7, 1941 the British Empire (in Hong Kong and Malaya) and simultaneously the USA (in the Philippines) and at Pearl Harbor, Hawaii). This led to the USA declaring war against Japan on December 8, 1941. The US then joined the British Empire, already at war with Germany since 1939, and its existing allies in the fight against the Axis powers.