Complex sentence: The Iraqi-based party was originally committed to Pan-Arabism (like its Syrian counterpart); after taking power in 1968 the party adopted Iraqi nationalism, and encouraging Iraqis to identify themselves as cultural heirs of Mesopotamia with a medieval-Islamic identity.
Split into simpler sentences: The Iraqi-based party was originally committed to' an-Arabism (like its Syrian counterpart). After taking power in 1968, the party adopted Iraqi nationalism and encouraging Iraqis to identify themselves as cultural heirs of Mesopotamia with a medieval-Islamic identity.