Muhammad Ali is a former World Heavyweight champion who became a leading voice for the rights of Blacks in the 1960s and '70s. Born Cassius Clay, he changed his name in 1964 when he joined the controversial Muslim sect, the Nation of Islam. Outside of the ring, he became popular for his showmanship and charisma. In 1967, he refused to fight in the Vietnam War, citing his religion and his opposition to U.S. policy. As a result, his boxing license was revoked and he was stripped of his title. The decision was later overturned and he regained his title, becoming the only three-time lineal champion.