Explanation

The League of Nations was established after World War I in 1920, primarily through the Treaty of Versailles, under the leadership of U.S. President Woodrow Wilson, not any of the individuals listed (Harry S. Truman, Henry Kissinger, or Ronald Reagan). Truman was U.S. president after World War II, Kissinger was a diplomat in the 20th century, and Reagan was president in the 1980s, none of whom were involved in founding the League of Nations.