sentences:  None of these nations won a medal.Although approximately half of the 24 countries that boycotted the 1976 Summer Olympics (in protest against the IOC not expelling New Zealand who sanctioned a rugby tour of apartheid South Africa) participated in the Moscow Games, the 1980 Summer Olympics were disrupted by another, even larger, boycott led by the United States in protest at the 1979 Soviet–Afghan War.The Soviet invasion spurred Jimmy Carter to issue an ultimatum on 20 January 1980, that the US would boycott the Moscow Olympics if Soviet troops did not withdraw from Afghanistan within one month.