The Ba'ath Party (Arabic اﻟﺒﻌﺚ) is the name of both the former ruling party of Iraq, headed by Saddam Hussein, and of the ruling party of Syria. After Saddam's regime was deposed in the 2003 Iraq war, the party was banned by American occupation forces in June 2003.
Both parties originate to the Ba'ath movement, an Arab political movement which started in the early 20th century with Syrian nationalists like Michel Aflaq and the more republican wing of Iraqi soldiers under British, and later Hashemite services.
Iraqi and Syrian Baathism didn't split until later. They actually were quite united throughout the period of Zionist ascendance in Palestine. There is much imitation of the Italian and Spanish Fascists by Baathists. Though it was extremely exclusive, factional and often relying on nationalist radicals in the militaries, Ba'ath always claimed to be speaking for the entire Arab nation and the progress of the masses.