Tin Oo joined the military on 26 February 1946 as a
second lieutenant in
Burma Rifles Battalion. He reached the ranks of
lieutenant on 7 January 1947,
captain on 27 September 1948 and served as executive officer at Armed Forces Training Headquarters. On 22 June 1949, he was transferred to No. 1 Burma Rifles Battalion as
company commander. He was promoted to the rank of
major on 25 January 1950 and became deputy
battalion commander (2IC) of the No. 1 Burma Rifles Battalion and took over the position of acting
battalion commander on 27 November 1952. Tin Oo was promoted to
lieutenant colonel on 21 January 1954 and became commander of the 4th
Infantry Brigade on 30 May 1957. He was then transferred to
Officers Training School, Bahtoo as
commandant on 13 September 1957. Throughout 1958 and 1961, he served as the battalion commander for the No. 14 Infantry Battalion (starting 18 November 1959) and No. 2 Burma Rifle Battalion (from 16 February 1962) and after his promotion as
colonel, he became acting commander for the No. 13 Infantry Brigade (from 20 February 1962). Tin Oo was then given the command of South West Regional Military Command and promoted to the rank of
colonel on 14 February 1964. On 19 September 1964, he became commander of Central Regional Military Command. He was then promoted to the rank of
brigadier general and became deputy chief of staff of the
Tatmadaw on 20 April 1972. On 8 March 1974 he was promoted to the rank of
general and became
commander in chief of the Tatmadaw. He was armed forces commander in chief during the
bloody crackdown on student protests surrounding the funeral of former UN Secretary-General
U Thant. During his military career, Tin Oo was awarded the
Thura medal, a prestigious award for gallantry and bravery in the face of the enemy that can be awarded to members of the
Myanmar Armed Forces. He led both tactical and strategic campaigns against the
Karen National Union as well as the
Communist Party of Burma and various ethnic armed groups, especially in the north and east of the country. == Forced retirement, accusations and imprisonment ==