Ba'athism, also spelled Baathism, is an Arab nationalist ideology which advocates the establishment of a unified Arab state through the rule of a Ba'athist vanguard party operating under a revolutionary socialist framework. The ideology is officially based on the theories of the Syrian intellectuals Michel Aflaq, Zaki al-Arsuzi, and Salah al-Din al-Bitar. Ba'athist leaders of the modern era include the former president of Iraq Saddam Hussein, and former presidents of Syria Hafez al-Assad and his son Bashar al-Assad.