Champion of Liberty commemorative stamps

Champion of Liberty commemorative stamps, also known as the Champion of Liberty series, were a series of nineteen commemorative stamps issued periodically by the United States Post Office between 1957 and 1961 in honor of men who fought for the cause of freedom and independence in their home countries. The stamp issues also served as a political and social statement against the perceived totalitarianism of the Soviet Union during the Cold War.

Source: Wikipedia — Champion of Liberty commemorative stamps (CC BY-SA 4.0)