Amethyst incident: The People's Liberation Army attacks HMS Amethyst (F116) travelling to the British embassy in Nanjing during the Chinese Civil War.

The Amethyst incident, also known as the Yangtze incident, was a historic event that occurred on the Yangtze River for three months in the summer of 1949, during the late phase of the Chinese Civil War. The incident involved the Communist People's Liberation Army (PLA), who were in the process of a river-crossing offensive to overthrow the Nationalist Government, and four British Royal Navy ships HMS Amethyst, HMS Black Swan, HMS Consort and HMS London. The British warships, whose claimed right of passage along the Yangtze had been unchallenged previously since the 1858 Treaty of Tientsin with the late Qing dynasty, came under bombardment by PLA artillery and were forced to withdraw permanently from Chinese territorial waters.

The People's Liberation Army (PLA) is the military of the Chinese Communist Party (CCP) and the People's Republic of China (PRC). It consists of four services—Ground Force, Navy, Air Force, and Rocket Force—and four arms—Aerospace Force, Cyberspace Force, Information Support Force, and Joint Logistics Support Force. It is led by the Central Military Commission (CMC) with its chairman as commander-in-chief.

HMS Amethyst was a modified Black Swan-class sloop of the Royal Navy. She was laid down by Alexander Stephen and Sons of Linthouse, Govan, Scotland on 25 March 1942, launched on 7 May 1943 and commissioned on 2 November 1943, with the pennant number U16. After the Second World War she was modified and redesignated as a frigate, and renumbered F116.

Nanjing is the capital of Jiangsu, a province in East China. The city, which is located in the southwestern corner of the province, has 11 districts, an administrative area of 6,600 km² (2,500 sq mi), and as of 2021 a population of 9,423,400. Situated in the Yangtze River Delta, Nanjing has a prominent place in Chinese history and culture, having served as the capital of various Chinese dynasties, kingdoms and republican governments dating from the 3rd century to 1949, and has thus long been a major center of culture, education, research, politics, economy, transport networks and tourism, being the home to one of the world's largest inland ports. The city is also one of the fifteen sub-provincial cities in the People's Republic of China's administrative structure, enjoying jurisdictional and economic autonomy only slightly less than that of a province. It has also been awarded the title of 2008 Habitat Scroll of Honor of China, Special UN Habitat Scroll of Honor Award and National Civilized City. Nanjing is also considered a Beta city classification, together with Chongqing, Hangzhou and Tianjin by the Globalization and World Cities Research Network, and ranked as one of the world's top 100 cities in the Global Financial Centres Index.