The Battle of Hong Kong (825 December 1941), also known as the Defence of Hong Kong and the Fall of Hong Kong, was one of the first battles of the Pacific War in World War II. On the same morning as the attack on Pearl Harbor, forces of the Empire of Japan attacked the British Crown colony of Hong Kong, without declaring war against the British Empire. The Hong Kong garrison consisted of British, Indian and Canadian units, also the Auxiliary Defence Units and Hong Kong Volunteer Defence Corps (HKVDC).

Within a week the defenders abandoned the mainland and less than two weeks later, with their position on the island untenable, the colony surrendered.

The Shanghai International Settlement (Chinese: 上海公共租界) originated from the merger in the year 1863 of the British and American enclaves in Shanghai, in which British subjects and American citizens would enjoy extraterritoriality and consular jurisdiction under the terms of treaties agreed by both parties. These treaties were abrogated in 1943.

The British settlements were established following the victory of the British in the First Opium War (1839–1842). Under the terms of the Treaty of Nanking, the five treaty ports including Shanghai were opened to foreign merchants, overturning the monopoly then held by the southern port of Canton (Guangzhou) under the Canton System. The British also established a base on Hong Kong. American and French involvement followed closely on the heels of the British and their enclaves were established north and south, respectively, of the British area.

Unlike the colonies of Hong Kong and Macau, where the United Kingdom and Portugal enjoyed full sovereignty in perpetuity, the foreign concessions in China remained under Chinese sovereignty. In 1854, the three countries created the Shanghai Municipal Council to serve all their interests, but, in 1862, the French concession dropped out of the arrangement. The following year the British and American settlements formally united to create the Shanghai International Settlement. As more foreign powers entered into treaty relations with China, their nationals also became part of the administration of the settlement. The number of treaty powers had climbed to a high of 19 by 1918 but was down to 14 by the 1930s: the United Kingdom, the United States, Japan, France, Italy, Norway, Sweden, Denmark, the Netherlands, Spain, Portugal, Peru, Mexico, and Switzerland.

Nonetheless, the SMC remained a predominantly British affair until the growth of Japan's involvement in the late 1930s. The international character of the Settlement was reflected in the flag and seal of the Municipal Council, which featured the flags of several countries.The international settlement came to an abrupt end in December 1941 when Japanese troops stormed in immediately following the Japanese attack on Pearl Harbor. In early 1943, new treaties signed formally ended the extraterritorial privileges of Americans and Britons, although its terms were not met until the recovery of Shanghai following Japan's 1945 surrender. The French later surrendered their privileges in a separate agreement in February 1946.

It was one of two Chinese international settlements, along with Gulangyu International Settlement.