"One of Leonhard's students at Yale was the future president George W. Bush, who wrote that Leonhard's History of the Soviet Union was "one of my most memorable courses," and "an introduction to the struggle between tyranny and freedom, a battle that has held my attention for the rest of my life.Leonhard was a visiting professor at the universities of Michigan at Ann Arbor in the United States; and Mainz, Trier, Kiel, Chemnitz, and Erfurt in both West Germany and the former East Germany.