He served in the Orange Free State and Transvaal in the Second Boer War, including fighting at the Battle of Diamond Hill.

[1] Haig's first military service came on 6 September 1890 when he was commissioned as a second lieutenant in the 3rd (Militia) Battalion of the South Wales Borderers.

[1][9][10] The 7th Dragoon Guards arrived at Southampton on 2 February to travel to South Africa for service in the Second Boer War.

[14] Fighting around the Klip River on 29 May, Haig saved another soldier whose horse had been shot, riding through artillery and rifle fire to rescue him.

[9][24] He was then promoted to lieutenant colonel on 4 July and on the same day given command of the 2nd Battalion of the Royal Berkshire Regiment in the 25th Infantry Brigade of 8th Division.

[26] Haig's battalion was relieved from the front on 10 October, and two days later the Berkshires were moved, along with the rest of the division, back to the Somme.

[30][31] After suffering high numbers of casualties from artillery bombardment, Haig began to send his companies forward to reinforce the attacking battalions.

At 3:50 a.m. on 24 October the Berkshires went in the first wave of a new attack on the trench (named "Zenith"), but the mud hindered them and they retreated under heavy rifle and machine gun fire at 4:30 a.m.

[34] Haig's battalion reorganised itself at Metigny between 20 November and 27 December, and 8th Division returned to the front line on 23 January 1917, based near Sailly-Saillisel.

The Berkshires successfully defeated the German counter attacks and by 6 March the area was secure; Haig's battalion was relieved on the same day.

[41] The British began to advance when the Germans retreated to the Hindenburg Line soon afterwards, and the Berkshires moved up to Hennois Wood on 26 March.

The retreating Germans left behind a rearguard at Sorel-le-Grand nearby, and on 30 March the battalion attacked the position, successfully capturing it while seeing very little of the enemy.

The battalion attacked through heavy snow with artillery support and successfully assaulted the German positions, and by daybreak Haig was able to go forward and establish defences on the edge of the wood.

[46] The following two weeks saw the Berkshires in reserve, helping to clear roads of obstacles; the Germans had attempted to destroy and block the routes of advance that the British might have used.

The success of this attack was due to the ability and energy with which he trained his battalion, made his preparations and handled the troops under his command during the battle.

Haig led this raid, made up of 168 men, entering the German trenches at around 1 a.m. and destroying a hastily set up enemy machine gun position.

25th Brigade was tasked with staying in reserve as the rest of the division attacked a line of trenches between Westhoek and the ruins of the Hooge railway station.

[55][56] Haig left the battalion under the command of his adjutant with whom they advanced until pinned down by counter attacks and heavy return fire, with units on the flanks of 8th Division failing to make the headway required to support it.

[Note 1] Haig never returned to his battalion, as some time early on in the day he was wounded by a bullet in the right thigh and evacuated to the rear.

[9][57][58] Haig returned to the Western Front in October and on 21 November was promoted to brigadier-general as commander of the 24th Infantry Brigade, also part of 8th Division.

[60][61] Military historian J. M. Bourne praises the appointment, describing Haig as "a man of great courage and leadership".

[64] The position was attacked heavily as part of Operation Michael, and by 25 March Haig had been forced to partially withdraw, making his new headquarters at Ablaincourt.

The division, with 24th Brigade one of two in the front line, repulsed the attack with heavy losses, but was forced to continue retreating because they were at risk of being cut off from the rest of the army, which had moved further back.

[66][67] The Germans managed to penetrate the right of the division's line, but were pushed back in a counter-attack by Haig's Sherwood Foresters, after which the front around them stabilised.

[68][69][66] Despite this the division was again at risk of being cut off because of failures to hold in other parts of the army, and on 28 March they fell back to between Vrely and Caix.

They left on 3 May for Champagne, where a confusion with the French commander in the sector meant that the British troops went straight into the front line.

[77][78] At 6 a.m. his headquarters at Berry-au-Bac was attacked heavily and overrun, and having been gassed in the assault, Haig and his brigade major only narrowly escaped capture.

[Note 3] Haig relinquished his command, due to his gassing and more general exhaustion, on 4 June, having taken no further part in the Battle of the Aisne because of his wounds.

[1][9] Early that year Haig planned to visit Sudan with Peter Haig-Thomas, chartering a steamship from the Sudanese government for the purpose.

[1][9] In retirement Haig was an avid golfer as a member of St Andrews Golf Club, in which he won several tournaments and was very well thought of.