On July 7, 1937, the Imperial Japanese Army charged on Chinese soldiers stationed near the Marco Polo Bridge outside Beiping, which finally transformed the regional conflict in Manchuria into an official war between the two nations. Beiping fell to the Japanese shortly afterwards, and Chang had to retreat to the southwest city of Chengdu with his colleagues to finish the work he had helped start.

One year later, the dropping of Japanese bombs in Chengdu forced them to move further south to Kunming, a city close to China’s border with French Indochina (now Vietnam). In 1940, during the nadir of war, the faculty at Tsinghua managed to establish a five-foot diameter wind tunnel in the mountains. Through the rest of the Second World War, this was the only operating wind tunnel in China that remained in Chinese hands. 

A Chinese soldier guarding the Marco Polo/Lugou bridge in July 1937.

Courtesy of China Plus