The Tokyo Olympics have been postponed a year to 2021 because of the coronavirus outbreak, but it's worth remembering that the games have been rocked by upheaval before.

Three other times, the games were canceled altogether because of World War I (1916) and World War II (1940 and 1944). The U.S. and several other countries boycotted the 1980 Olympics in Moscow, but the games still went on.

A look at the Olympic Games that never were.