During the Suez Crisis of 1956, future prime minister Lester B. Pearson eased tensions by proposing the inception of the United Nations Peacekeeping Force, for which he was awarded the 1957 Nobel Peace Prize. As this was the first UN peacekeeping mission, Pearson is often credited as the inventor of the concept. Canada has since served in over 50 peacekeeping missions, including every UN peacekeeping effort until 1989, and has since maintained forces in international missions in Rwanda, the former Yugoslavia, and elsewhere; Canada has sometimes faced controversy over its involvement in foreign countries, notably in the 1993 Somalia affair.