Burma Campaign and North African theatre as part of the Norfolk Regiment of the British Indian Army. In Middle East, he led the company and was listed in mentioned in despatches for "distinguished services in the Middle East during the period February to July 1941" and in the London Gazette 30 December 1941 as a Lieutenant and acting Major. In 1942, his heroic action for valor won him the praise and was appointed as Member of the Order of the British Empire (MBE) for "gallant and distinguished services in the Middle East." In 1945, he was promoted as substantive captain and substantive major in 1946 and was serving with the Machine Gun battalion, 13th Frontier Force Rifles by October 1942. During his time at the Indian Military Academy, Musa was selected as part of the first batch of cadets. Called "The Pioneers", his class also produced Smith Dun and Sam Manekshaw, future army chiefs of Burma and India, respectively. After the partition of British India that followed the establishment of Pakistan in 1947, he opted for Pakistan and joined the Pakistan Army as a staff officer. In 1947 in the acting rank of Brigadier, he commanded the 103rd Infantry Brigade based in Sialkot brigade in Kashmir and served as commander of military units in the first war with India. In 1948, he went on to command the 52nd Infantry Brigade positioned in Quetta. After the war in 1948, Musa studied and graduated from the Command and Staff College in Quetta and proceeded to attend the Imperial Defence College in United Kingdom prior to his graduation. Later military career In 1950s, Musa's commanding assignments included his role as the Commandant of the East Pakistan Rifles, and also having served as GOC of 14th Infantry Division in Dhaka, East Pakistan, in 1951. In 1952, his last field assignment included his role as General Officer Commanding (GOC) of 8th Infantry Division positioned in Quetta before stationed at the GHQ. Later, he soon became the Chief of Staff of the Pakistan Army (then the commander-in-chief of the army's deputy) in the rank of major-general at the Army GHQ. His career progressed well in the army and was ascended as Commander-in-Chief by President Ayub Khan in 1958 when the latter disposed President Iskander Mirza who imposed martial law in 1958. Musa's promotion to the four-star appointment came with controversy in the country as many saw