Field Marshal Sir Archibald James Halkett Cassels, GCB, KBE, DSO (28 February 1907 – 13 December 1996) was a senior British Army officer who served as Chief of the General Staff (CGS), the professional head of the British Army, from 1965 to 1968. As a young man he was a first-class cricket player, initially playing in India for the Europeans against the Hindus in the Lahore Tournament and going on to play for a Punjab Governor's XI against Northern India team and for a Viceroy's XI against the Roshanara Club. He later played for the British Army cricket team against the RAF at The Oval and then played for the Egyptian national side against HM Martineau's XI in Alexandria.

Cassels served in the Second World War as commander of the 152nd Infantry Brigade, commanding the brigade during Operation Goodwood, Operation Totalize and Operation Veritable, before becoming General Officer Commanding 51st (Highland) Division in the closing stages of the war. He later commanded the 1st Commonwealth Division in the Korean War and was General Officer Commanding of the 1 (British) Corps before becoming director of operations in Malaya during the Malayan Emergency.

Cassels went on to be commander, Northern Army Group, then General Officer Commanding Eastern Command and then Commander-in-Chief (C-in-C) of the British Army of the Rhine (BAOR). As Chief of the General Staff, he advised the British government on the implementation of the 1966 Defence White Paper.

James Cassels was born in Quetta, British India (now Pakistan), on 28 February 1907, the son of Robert Cassels (later General Sir Robert Cassels), a British Indian Army officer, and Florence Emily Cassels (née Jackson).^[2] Upon being sent to England, he was educated at Rugby School and, later, at the Royal Military College, Sandhurst, where he won the Sword of Honour.^[3] Upon Passing out from Sandhurst, Cassels was commissioned as a second lieutenant into the Seaforth Highlanders, a line infantry regiment of the British Army, on 30 August 1926.^[4] He was posted to Central India with the 2nd Battalion of his regiment in 1928 and, having been promoted to lieutenant on 20 August 1929, was appointed aide-de-camp (ADC) to his father in May 1930.^[5] He became adjutant of the 2nd Battalion, Seaforths, then serving in England and commanded by Lieutenant Colonel Sir John Laurie, who would feature numerous times in his career, in March 1934 and was promoted to captain on 22 March 1938.^[5]

A right-handed batsman and right-arm fast-medium/Off spin bowler,^[6] he played first-class cricket between 1928 and 1935^[7] and also represented the Egyptian national team.^[8]

His first recorded match came in 1921 when he played for his school team against Marlborough College at Lord's.^[9] His first-class debut was in 1928 when he played for the Europeans against the Hindus in the Lahore Tournament, a tournament similar to the more famous Bombay Quadrangular Tournament but played in Lahore, then a part of India. He played for a Punjab Governor's XI against Northern India team in his second first-class match later that month, also in Lahore.^[7] He took 6/51 in the second innings of that match,^[10] his best innings bowling performance in first-class cricket.^[6]

He played his next first-class match in Delhi in February 1932, playing for a Viceroy's XI against the Roshanara Club. He played his first first-class match in England that June, playing for the British Army cricket team against the RAF at The Oval,^[7] making his highest first-class score of 72.^[11] The following year he played for the Egyptian national side against HM Martineau's XI in Alexandria, taking five wickets in the second innings of the visitors.^[12]

He played his final first-class match in the 1935 English season, playing for the Army against Cambridge University.^[7] He continued to play cricket at a lower level, playing for Delhi against Lord Tennyson's XI in 1938. After the war, he played twice for the Army against the Royal Navy, in 1948 and 1949, and against Cambridge University in 1949.^[9]

After the war he continued to command the 51st Division in Germany until March 1946 when he selected to command the 6th Airborne Division. The division, which had fought with distinction in Northwest Europe, was then serving in Palestine during the Palestine Emergency (for further information see 6th Airborne Division in Palestine).^[20] Cassels's time there was not altogether happy. "I was in Palestine from March 1946 until the end of the year, ten hellish months. I got appallingly rude letters from America, saying that I was much worse than Hitler, addressed to me personally. We nearly had seizures every time we read a newspaper. The general line was that we were anti-semitic beasts and murderers. I don't think they realized that many of my men had parachuted into Normandy in June 1944. Large numbers of them were killed and wounded fighting to remove Hitler from the face of the earth."^[21] "It did make one hopping mad to see some of the comments in the Press...denigrating all or most of our actions. They sat in comfort and safety in England while we lived in fairly uncomfortable conditions and under the continued...threat of being blown up!!"^[22]

He relinquished command of the division to Major General Eric Bols in early 1947 to return to England, where he attended the prestigious Imperial Defence College. For his services in Palestine he was mentioned in despatches.^[23] Promoted to the substantive rank of colonel on 19 August 1947,^[24] he became Director of Land / Air Warfare at the War Office in January 1948.^[20] Having been promoted to brigadier on 4 March 1948^[25] and to major general on 20 December 1948,^[26] he became Chief Liaison Officer with the United Kingdom Services Liaison Staff at Melbourne in Australia on 16 December 1949^[27] and was appointed a Companion of the Order of the Bath in the New Year Honours 1950.^[28] He became the first GOC of the 1st Commonwealth Division in July 1951 during the Korean War^[20] for which he was awarded the Legion of Merit in the Degree of Commander by the U.S. President, Harry S. Truman on 16 September 1952^[29] and appointed a Knight Commander of the Order of the British Empire on 10 October 1952.^[30]

He was made GOC of the 1 (British) Corps on 4 January 1953^[31] and, having been promoted to the rank of lieutenant-general on 2 February 1954,^[32] became Director of Military Training at the War Office on 15 November 1954.^[33] He was appointed director of operations in Malaya on 17 September 1957 during the Malayan Emergency^[34] and, having been promoted to full general on 29 November 1958,^[35] became General Officer Commanding-in-Chief (GOC-in-C) for Eastern Command on 29 June 1959.^[36] He commanded the Northern Army Group and was Commander-in-Chief (C-in-C) of the British Army of the Rhine (BAOR) on 7 January 1960^[37] and, having advanced to Knight Grand Cross of the Order of the Bath in the New Year Honours 1961,^[38] became Adjutant-General to the Forces on 1 June 1963.^[39] He became Chief of the General Staff (CGS), the professional head of the British Army, on 8 February 1965^[40] and advised the British government on the implementation of the 1966 Defence White Paper which, inter alia, established the Territorial and Army Volunteer Reserve (TAVR). He was promoted to field marshal on 29 February 1968 on his retirement from the British Army.^[41]

He was also colonel of the Seaforth Highlanders (Ross-shire Buffs, The Duke of Albany's) from 15 March 1957^[42] and Colonel Commandant of the Royal Military Police from 27 May 1957.^[43] He was also a member of the Committee of the Marylebone Cricket Club.^[2]

His interests included fishing, dance music, playing the guitar and the clarinet and playing various sports including cricket, polo and golf.^[2] He died at Newmarket in Suffolk on 13 December 1996.^[2]

In 1935 he married Joyce Kirk; they had one son.^[5] Following the death of his first wife, he married Joy Dickson in 1978.^[41]