After World War II, Pan-Arabism sought to unite all Arabic-speaking countries into one political entity. Only Syria, Iraq, Egypt, Sudan, Tunisia, Libya and North Yemen considered the short-lived unification of the United Arab Republic. Historical divisions, competing local nationalisms, and geographical sprawl were major reasons for the failure of Pan-Arabism. Arab Nationalism was another strong force in the region which peaked during the mid-20th century and was professed by many leaders in Egypt, Algeria, Libya, Syria, and Iraq. Arab Nationalist leaders of this period included Gamal Abdel Nasser of Egypt, Ahmed Ben Bella of Algeria, Michel Aflaq, Salah al-Din al-Bitar, Zaki al-Arsuzi, Constantin Zureiq and Shukri al-Kuwatli of Syria, Ahmed Hassan al-Bakr of Iraq, Habib Bourguiba of Tunisia, Mehdi Ben Barka of Morocco, and Shakib Arslan of Lebanon.