1940　 Games of the XII Olympiad in Tokyo (Japan)

The 12th Games were planed to be held in Tokyo, but were retracted due to the outbreak of the Second Sino-Japanese War in 1937. The IOC then chose Helsinki (Finland) as the host city instead, but when World War II broke out, the Summer Games were finally cancelled.
Helsinki eventually held the 1952 Summer Olympics and Tokyo the 1964 Summer Olympics.