Abu Ubaidah ibn al-Jarrah
After the end of the Ridda wars in the Arabian Peninsula, Abu Bakr sent four armies to the Levant, led by Yazid ibn Abi Sufyan, Abu Ubaidah ibn al-Jarrah, Amr ibn al-Aas, and Shurahbil ibn Hasana. Because of the strength and size of the armies of the Byzantine Empire, Abu Bakr ordered Khalid ibn al-Walid to march with half of the Iraqi army to the Levant and command the armies there.