William Slim was born in Bishopston, near Bristol on 6 August 1891, the son of John Slim, a hardware merchant and his wife, Charlotte Slim (nee Tucker). He was educated at St Philip's School, Edgbaston and King Edward's School, Birmingham, 1903-10, where he joined the Officer's Training Corps. He married Aileen Robertson in 1926 (died 1993), with whom he had one son, John, and one daughter, Una.
He was first employed as an elementary teacher and then as a clerk at an engineering firm, Steward and Lloyds from 1910-14, joining Birmingham University Officers' Training Corps in 1912. He was commissioned in the Royal Warwickshire Regiment with the rank of temporary Second Lieutenant in 1914 and was sent to fight at Gallipoli. He was wounded in action at the Battle of Sari Bair Ridge in August 1915. After a period of convalescence in Britain, he returned to action in Mesopotamia, where he fought for the next six months and was awarded a Military Cross in 1916.
Wounded again in Mesopotamia in 1917, Slim was evacuated to India. He spent two years on the staff of the army headquarters, where he was made a temporary Major in the 6th Gurkha Rifles in November 1918. He transferred again to the British Indian Army as Captain in May 1919, and found himself surrounded by officers from a similar background to his own. He became adjutant of the battalion and was stationed at Abbottabad.
Slim obtained professional training for higher command at the Indian Staff College, Quetta, in 1926. He returned to Army Headquarters as a staff officer from 1929 1933, when he was promoted to the rank of Major. He spent from 1934 1936 as an instructor at the Staff College, Camberley and was a student at the Imperial Defence College in 1937. Before returning to regimental soldiering in 1938 he spent time at the Senior Officers' School in Belgaum.
Slim was now familiar with the debates over mobility and army doctrine which divided British military opinion during the interwar years. He returned to soldiering as Commander of the 2nd battalion, 7th Gurkha Rifles at Shillong in Assam. To support his wife and young children Slim supplemented his salary by writing fiction and articles under the pen-name 'Anthony Mills'.
The eruption of the Second World War in 1939 saw him promoted to Brigade Commander, leading the 10th Indian Brigade in Sudan and Eritrea in 1940 1941, where he was wounded again. He presided over the occupation of Persia in August 1941 as commander of the 10th Indian Division in Iraq, Syria and Persia. He led what became the longest withdrawal in British military history of the 1st Burma Corps to the Imphal Plain in eastern Assam.
He returned to action commanding the 15th Burma Corps in March-June 1942. Unfortunately, Slim was brought in too late to the disastrous first Akran campaign and he suffered a difficult relationship with Lieutenant-General N. M. S. Irwin. Irwin was soon replaced by General Sir George Giffard, who would strongly support Slim over the next few months.
Their arrival was part of a wider restructuring of the Eastern theatre. Slim and Giffard were joined by the new Commander-in-Chief in India, General Sir Claude Auchinleck and by Vice-Admiral Lord Louis Mountbatten heading up the new south-east Asia Command (SEAC). Giffard took lead of the Eleventh Army, while Slim became commander of the principal operational formation, the Fourteenth Army. He was awarded a CBE in October 1942.
Slim and his troops were able to overcome the Japanese attack at Arakan (1942-1943), where victory came to be a significant turning point in the Burmese theatre. Commanding both the Arakan and Imphal battlefields Slim conducted 'the most complex, geographically sprawling battled presented by any British army commander in either world war'. [ODNB ref] Slim was awarded a DSO in January 1943.
Slim turned his attention to recapturing Burma, overland, and from the north in the 1944-1945 dry season. His plan, 'Capital' was a successful gamble and he relied entirely on air supply to support the Fourteenth Army over their 300-mile offensive, demonstrating his astute understanding of the power of mobility.
By May 1945, SEAC had been restructured to encompass allied land forces, and now the new ALFSEA was headed by General Sir Oliver Leese. Differing wartime experiences meant for a tense relationship between ALFSEA and the Fourteenth Army and in a bizarre episode involving Leese, Slim was nearly removed from the leadership of his unit. However, intervention from both London and New Delhi meant that Slim was promoted, having been made a General in July 1945, to Commander-in-Chief of ALFSEA in August 1945.
On the 1st January 1946 Slim was knighted GBE and took up his new position of Commandant of the Imperial Defence College. He was made Aide-de-Camp to the King in February 1947 and he refused offers from both India and Pakistan to become Commander-in-Chief of their armies, and instead became Deputy Chairman of the Railway Executive in April 1948. But Slim's hiatus from the army was not to last long: by November 1948 Slim became the first Indian Army officer to be appointed as Chief of the Imperial General Staff (CIGS) in January 1949, with the full ranking of Field Marshal.
After a full tour as CIGS, Slim was awarded the GCMG in December 1952 and KStJ in January 1953 after which took up his new position as the Governor-General of Australia in May 1953. He was awarded the GCVO in February 1954.
Slim retired from public duty to Britain in 1959, and soon after published his memoirs Unofficial History. His personal narrative of the Burma campaign, Defeat into Victory (1956) had already been a resounding success and is still widely considered to be one of the most important memoirs written by a prominent military leader. In April 1959 he was appointed a Knight of the Garter and was raised to the peerage in July 1960, becoming Viscount Slim of Yarralumla in the Capital Territory of Australia and of Bishopston in the City and County of Bristol. After a number of places on the boards of successful UK companies, Slim was appointed Governor and Constable of Windsor Castle in July 1964. He remained in office until his death on 14th December 1970. He was survived by his wife, Aileen and children, Una and John (who succeeded him in the peerage).
Papers comprising manuscripts of books, articles, lectures, letters, diaries, press cuttings and photographs.
The papers were collected by William Slim's biographer, Ronald Lewin, and given to Churchill Archives Centre by Slim's wife, Aileen, Viscountess Slim, and son, Viscount Slim, and other donors, 1977-2011.