The 1940 Summer Olympics, officially known as the Games of the XII Olympiad, was a planned international multi-sport event scheduled to have been held from 21 September to 6 October 1940, in Tokyo City, Japan, and later rescheduled for 20 July to 4 August 1940, in Helsinki, Finland following the outbreak of the Second Sino-Japanese War in 1937.

While both Tokyo officials and International Olympic Committee (IOC) representatives were behind the campaign, the national government, which was ever more interested in military matters, did not have any strong supporters for such a diplomatic gesture.

[3] When the Second Sino-Japanese War broke out on 7 July 1937, Ichirō Kōno, a member of the Imperial Diet (legislature), immediately requested that the Olympics be forfeited.

[6] In March 1938, the Japanese provided reassurances to the IOC at the organization's Cairo conference that Tokyo would still be able to serve as the host city.

However, many Diet members in Japan had already openly questioned hosting the Olympics in wartime, and the military was demanding that the organizers build the venues from wood because they needed metals for the war front.

[7] In July, a legislative session was held to decide the matters of the Summer and Winter Olympics and the planned 1940 World's Fair all at once.

He closed his speech saying, "When peace reigns again in the Far East, we can then invite the Games to Tokyo and take that opportunity to prove to the people of the world the true Japanese spirit.

A feature film, Olimpiada '40, produced by the director Andrzej Kotkowski in 1980 tells the story of these games and of one of the prisoners of war, Teodor Niewiadomski.