Rawlinson was born in Westminster, London. His father, Sir Henry Rawlinson, 1st Baronet, was an Army officer, and a renowned Middle East scholar who is generally recognised as the father of Assyriology. Rawlinson attended Eton College and the Royal Military College, Sandhurst, and entered the Army as a lieutenant in the King's Royal Rifle Corps in India on 6 February 1884. His first military experience was serving in Burma during an 1886 uprising.
In 1889, Rawlinson's mother died and he returned to Britain. He transferred to the Coldstream Guards and was promoted to captain on 4 November 1891. He served on General Herbert Kitchener's staff during the advance on Omdurman in Sudan in 1898, and was promoted to major on 25 January 1899 and to brevet lieutenant-colonel on 26 January 1899.
Rawlinson served with distinction in a field command in the Second Boer War from 1899 to 1902, earning promotion to the local rank of colonel on 6 May 1901. He was in Western Transvaal during early 1902, and lead a column taking part in the Battle of Rooiwal, the last battle of the war (11 April 1902). Following the end of hostilities in June 1902, he returned to the United Kingdom together with Lord Kitchener on board the SS Orotava, which arrived in Southampton on 12 July. In a despatch dated 23 June 1902, Lord Kichener wrote of Rawlinson that he "possesses the qualities of Staff Officer and Column Commander in the field. His characteristics will always ensure him a front place in whatever he sets his mind to." He received the brevet rank of colonel in the South Africa Honours list published on 26 June 1902, was promoted to the substantive rank of colonel on 1 April 1903, and named as commandant of the Army Staff College. Promoted to temporary brigadier-general on 1 March 1907, he was made Commander of 2nd Infantry Brigade at Aldershot that year and, having been promoted to major-general on 10 May 1909, he became General Officer Commanding 3rd Division in 1910.
Shortly after the outbreak of the First World War in 1914, Rawlinson was appointed General Officer Commanding 4th Division in France. Promoted to temporary lieutenant-general on 4 October 1914, he then took command of the IV Corps. Rawlinson wrote to the Conservative politician Lord Derby (24 December 1914) forecasting that the Allies would win a war of attrition, but it was unclear whether this would take one, two or three years.
At the end of 1915, Rawlinson was considered for command of British First Army, in succession to Douglas Haig, but the command was instead given to Sir Charles Monro. He was promoted to temporary general on 22 December 1915. Promoted to the substantive rank of lieutenant-general on 1 January 1916, Rawlinson assumed command of the new Fourth Army on 24 January 1916. as the planned Allied offensive on the Somme. He wrote in his diary: "It is not the lot of many men to command an army of over half a million men." The Somme was originally conceived as a joint Anglo-French offensive, but owing to the demands of the Battle of Verdun, French participation was greatly reduced, leaving the British, and especially Rawlinson's inexperienced army, to bear the brunt of the offensive. Nevertheless, on the eve of the offensive, he "showed an attitude of absolute confidence."
The Somme offensive was launched on 1 July 1916. It soon became a heavy defeat, with British forces repulsed by the Germans along most of the front, with the British sustaining nearly 60,000 casualties on the first day. The heaviest defeats were in Rawlinson's own sector, in front of Pozières and Thiepval. By the afternoon Rawlinson was aware of the scale of the disaster. On the Allied right, the British and French had more success, but Rawlinson would not allow the corps commander, General Walter Congreve, to advance beyond his set objectives: a decision for which he was later criticised.
The principal cause of the defeat, however, was the Army's misplaced belief that the long and heavy preliminary artillery barrage had destroyed the German barbed wire and trenches. In fact, the German trenches were largely intact, and heavily laden British infantry were required to advance at a slow walk, across a maze of shell holes, into concentrated German machine-gun fire. After the war Rawlinson was held responsible for the tactics followed on 1 July 1916. The historian Martin Middlebrook wrote: "What is certain is that those divisions, Regular or otherwise, which most closely followed Rawlinson's advice, suffered the heaviest casualties and achieved the least success." As the disaster unfolded, however, it was too late for either Haig or Rawlinson to change the set plan.
The full extent of British casualties on the Somme were not known to the public until after the war: even Haig and Rawlinson were not fully aware of them. The blame for the defeat was directed mainly at divisional and corps commanders: but only two, Major-General Edward Stuart-Wortley and Major-General Thomas Pilcher, were dismissed. Both were dismissed for not driving their units hard enough - that is for not creating more casualties, rather than for causing too many. To dismiss Rawlinson would have been to admit that the Somme offensive had been defeated, and that it had been incompetently planned and executed, which neither Haig nor the British government was willing to do. Middlebrook writes: "Haig and Rawlinson were protected by the sheer enormity of the disaster."
Middlebrook holds Rawlinson principally responsible for the heavy British casualties on the Somme: "Rawlinson was not to blame for the shortage of heavy artillery, but he had failed to recognise the depth and strength of the German dug-outs it was supposed to destroy. He ignored the doubts of infantry officers on this score... By insisting on his own rigid attack plan he robbed his men of any opportunity to use the intelligence and initiative which they surely possessed. Rawlinson must take full responsibility for this, the worst mistake of the day and the one which had caused most of the casualties."
In January 1917, Rawlinson was promoted to permanent General "for distinguished service in the field". For a period in 1917–18, he also commanded the Second Army. In February 1918 he was appointed British Permanent Military Representative to the inter-Allied Supreme War Council at Versailles.
Rawlinson returned to the Fourth Army in July 1918 for the Allied counter-offensive. By this time the German Army's great spring offensive, Operation Michael, had been checked, and the Allies were preparing a counter-offensive. Following the success of the Australian attack at Le Hamel on 4 July, Haig entrusted Rawlinson with planning a larger attack, designed to force the Germans back from the city of Amiens, and also further to damage the German Army's weakening morale. Rawlinson had learned from his experiences on the Somme. "The immeasurable superiority of the planning for 8 August 1918 over that for 1 July 1916 testified to the distance the BEF had travelled in the interim." The attack was to be on a relatively narrow front, with no prior bombardment and limited objectives. To ensure a breakthrough, Haig gave Rawlinson command of virtually the whole British armoured forces. By this stage of the war British manpower was severely depleted, and Rawlinson relied heavily on Australian, Canadian and American troops to achieve the breakthrough.
The Allies achieved complete surprise, and the Battle of Amiens proved a striking success. On 8 August, described by General Erich Ludendorff as "the black day of the German Army", the Allies took 12,000 prisoners and captured 450 guns. Both the German and Allied commands were struck by the collapse in German morale and the high number of Germans surrendering without a fight. Nevertheless, the Allies were still cautious about pressing their advantage too far: on 11 August Rawlinson advised Haig to halt the offensive.
In September, again commanding a mixed force of British, Australian and American divisions, Rawlinson led his Army in the Hundred Days Offensive, the successful Allied effort to break through the Hindenburg Line of German defences. Rawlinson daringly ordered the Canadian commander, General Arthur Currie, to cross the Canal du Nord, a key part of the German defences. The resulting Battle of Canal du Nord saw the Germans decisively defeated. By 30 September, a 50 kilometre stretch of the Hindenburg Line had been taken, and the Germans were in full retreat.
Rawlinson received many honours. He was made GCVO in 1917 and KCMG 1918. Following the Armistice, Parliament passed a vote of thanks to him for his service. In 1919, he was raised to the peerage as Baron Rawlinson of Trent in the County of Dorset, and appointed a Knight Grand Cross of the Order of the Bath (GCB). He was again called on to organise an evacuation, this time of the Allied forces that had been sent to Russia to intervene in the Russian Civil War. In November 1919 he became General Officer Commanding-in-Chief for Aldershot Command. In 1920, Rawlinson was made Commander-in-Chief, India, a post he held until his death. In 1924, he was appointed a Knight Grand Commander of the Order of the Star of India (GCSI). He died in Delhi on 28 March 1925 when he was taken ill after playing polo and cricket.
Henry Rawlinson's brother Alfred Rawlinson also played a significant role during World War I, but this was mostly confined to the Middle Eastern theatre in Turkey, Mesopotamia and Persia. He was taken prisoner of war by the Turks, which caused some political complications based on his brother's position. The story is contained in his book, Adventures in the Near East, 1918-1922.Knight Grand Cross of the Royal Victorian Order (GCVO) - 14 July 1917 (KCVO: 15 August 1916; CVO: 30 June 1905)
Knight Commander of the Order of St. Michael and St. George (KCMG) - 1 January 1918
Knight Grand Cross of the Order of the Bath (GCB) - 1 January 1919 (KCB: 18 February 1915; CB: 1902)
Baron Rawlinson, of Trent in the County of Dorset - 31 October 1919
Grand Officer of the Legion of Honour of France - 24 February 1916
Order of Danilo, 1st Class of the Kingdom of Montenegro - 31 October 1916
Obilitch Medal in Gold of the Kingdom of Montenegro - 21 April 1917
Order of St. George, 4th Class of the Empire of Russia - 1 June 1917
Grand Officer of the Order of Leopold of Belgium - 26 July 1917
Croix de Guerre of Belgium - 11 March 1918
Croix de Guerre of France - 11 March 1919
American Army Distinguished Service Medal - 12 July 1919