Wellington was commissioned a second lieutenant in the Territorial Army in 1936, and was commissioned with the same rank (on probation) in the British Army Reserve in 1939.
 In 1940, he was given a full commission as a second lieutenant in the Royal Horse Guards Regiment, with the service number 68268.
 He served in the Second World War with the 1st Household Cavalry Regiment in the Middle East and Italy, during which time he was awarded the Military Cross, and promoted to the war substantive rank of captain.
 Following the war, the 1st Household Cavalry Regiment disbanded, and he returned to Royal Horse Guards, where he was promoted to lieutenant in 1946, and advanced to the rank of captain later that year.
 He received successive promotions to major in 1951, and to lieutenant colonel in 1954, rising to command of his regiment.
Seeing service in Cyprus between 1956 and 1958, he was appointed an Officer of the Order of the British Empire in 1958.

He then moved to the Household Cavalry Regiment, which he began commanding in 1959.
 Promoted to colonel in 1960, he commanded the 22nd Armoured Brigade (1960–1961), served  as Commander, Royal Armoured Corps in the I(BR) Corps of the British Army of the Rhine, and became defence attaché to Spain in 1964.
 He retired from the Army in 1968 and was granted the honorary rank of brigadier.
Wellington was commissioned a second lieutenant in the Territorial Army in 1936, and was commissioned with the same rank (on probation) in the British Army Reserve in 1939.  In 1940, he was given a full commission as a second lieutenant in the Royal Horse Guards Regiment, with the service number 68268.  He served in the Second World War with the 1st Household Cavalry Regiment in the Middle East and Italy, during which time he was awarded the Military Cross, and promoted to the war substantive rank of captain.  Following the war, the 1st Household Cavalry Regiment disbanded, and he returned to Royal Horse Guards, where he was promoted to lieutenant in 1946, and advanced to the rank of captain later that year.  He received successive promotions to major in 1951, and to lieutenant colonel in 1954, rising to command of his regiment. Seeing service in Cyprus between 1956 and 1958, he was appointed an Officer of the Order of the British Empire in 1958.
He then moved to the Household Cavalry Regiment, which he began commanding in 1959.  Promoted to colonel in 1960, he commanded the 22nd Armoured Brigade (1960–1961), served  as Commander, Royal Armoured Corps in the I(BR) Corps of the British Army of the Rhine, and became defence attaché to Spain in 1964.  He retired from the Army in 1968 and was granted the honorary rank of brigadier.
Valerian Wellesley, 8th Duke of Wellington