World War II: Four thousand Chongqing residents are asphyxiated in a bomb shelter during the Bombing of Chongqing.

Chongqing is a direct-administered municipality in Southwestern China. Chongqing is one of the four direct-administered municipalities under the Central People's Government, along with Beijing, Shanghai, and Tianjin. It is the only directly administrated municipality located deep inland. The municipality covers a large geographical area roughly the size of Austria, which includes several disjunct urban areas in addition to Chongqing proper. Due to its classification, the municipality of Chongqing is the largest city proper in the world by population, though Chongqing is not the most populous urban area.

Asphyxia or asphyxiation is a condition of deficient supply of oxygen to the body which arises from abnormal breathing. Asphyxia causes generalized hypoxia, which affects all the tissues and organs, some more rapidly than others. There are many circumstances that can induce asphyxia, all of which are characterized by the inability of a person to acquire sufficient oxygen through breathing for an extended period of time. Asphyxia can cause coma or death. In 2015, about 9.8 million cases of unintentional suffocation occurred which resulted in 35,600 deaths. The word asphyxia is from Ancient Greek α- "without" and σφύξις sphyxis, "squeeze".

The bombing of Chongqing, from 18 February 1938 to 19 December 1944, was a series of massive terror bombing operations authorized by the Empire of Japan's Imperial General Headquarters and conducted by the Imperial Japanese Army Air Service (IJAAF) and Imperial Japanese Navy Air Service (IJNAF). Resistance was put up by the Chinese Air Force and the National Revolutionary Army's anti-aircraft artillery units in defense of the provisional wartime capital of Chongqing and other targets in Sichuan.