German political author, publicist, and historian.

A former communist who fled to the Soviet Union in 1935, he became part of the "National Committee for the liberation of Germany". In 1945, he came back to East Germany as part of the "Ulbricht group", a special command of politicians and instructors.

In 1949, Leonhard defected from the Soviet Union and fled first to Yugoslavia and later to West Germany. Later he became a lecturer for the Columbia University and the Yale University as an expert on the Soviet Union.

In 1950 he co-founded the short lived Titoist Independent Workers Party Germany (UAPD) which has funded by Yugoslavia.