Al-Askari served in the Ottoman Army during World War I until he was captured by British forces attacking the Empire from Egypt. After he was released he was converted to the cause of Arab nationalism and joined forces with Amir Faisal and T. E. Lawrence (Lawerence of Arabia), with his brother-in-law, Nuri as-Said, who would also serve as prime minister of Iraq. Al-Askari took part in the conquest of Damascus in 1918 and supported placing Faisal on the Syrian throne. When Faisal was deposed by the French in 1920, he advocated granting him a new throne in Iraq.