Perhaps his most famous fight was his one-round knockout of Max Schmeling , the German former heavyweight champion , in 1938 . Schmeling had given Louis his only loss up to that point , and was widely seen at that time as a representative of Nazi Germany . When Schmeling arrived in New York in June , 1938 for the rematch , he was accompanied by a Nazi party publicist who issued statements that a black man could not defeat Schmeling , and that when Schmeling won , his prize money would be used to build tanks in Germany .