22 August 1972
The International Olympic Committee (IOC) asked Rhodesia (now Zimbabwe) to withdraw from the 20th Olympic Summer Games held in Munich, Germany. The request came a few days before the official opening ceremony, as result of Rhodesia's racial policy. The IOC felt the policy of only allowing black athletes to compete in sprinting and jumping events did not make competition fair for white athletes competing for other nations. More than 7,000 athletes participated, representing 122 countries. The 1972 Olympic Games will probably be best remembered for the murder of eleven Israeli athletes by Palestinian terrorists.    
References

Pretoria News, Friday August 22, 2003. Today in History|Rosenberg Jennifer, History of the Olympics, [online], Available at history1900s.about.com [Accessed: 20 August 2013]|Olympics Website, Munich 1972: 26 August- 11 September, [online], Available at www.olympic.org [Accessed: 20 August 2013]