He was present at the Battle of Isandlwana during the Anglo-Zulu War on 22 January 1879, serving with the British invasion force as a transport officer for a detachment of Royal Artillery.

As the Zulu impis overwhelmed the British lines, destroying it in hand-to-hand fighting, Smith-Dorrien narrowly escaped on his transport pony over 20 miles of rough terrain with twenty Zulu warriors in running pursuit, crossing the Buffalo River, 80 yards wide and with a strong current, by holding the tail of a loose horse.

[8] Because of his conduct in trying to help other soldiers escape from the battlefield, including a colonial commissariat officer named Hamer whose life he saved, he was recommended for the Victoria Cross, but it was not awarded.

[8] His observations on the difficulty of opening ammunition boxes led to changes in British Army practice for the rest of the war (though modern commentators argue that this was not as important a factor in the defeat as was thought at the time).

He was promoted captain on 1 April 1882, appointed assistant chief of police in Alexandria on 22 August 1882, then given command of Mounted Infantry in Egypt on 3 September 1882, and was seconded to the Egyptian army (1 February 1884).

[12] On 31 October 1899, he shipped to South Africa for the Second Boer War, arriving at Durban 13 December 1899, in the middle of "Black Week".

This did not endear him to the arme blanche ('pro-cavalry') faction, which included French and Douglas Haig, and whose views prevailed after the retirement of Lord Roberts.

He abandoned the practice of posting pickets to trawl the streets for drunk soldiers outside the base, more than doubled the number of playing fields available to the men, cut down trees, and built new and better barracks.

His reforms earned many plaudits but were treated as an implied criticism by his predecessor, Sir John French, with whom he had still been on relatively cordial terms at the end of the South African War.

He had experience of dealing with Territorials (who would make up much of II Corps in 1914) for the first time and instigated training on fire-and-movement withdrawals which would also prove useful at Le Cateau.

[12] Although Smith-Dorrien was perfectly urbane and, by the standards of the day, kind-hearted towards his troops, he was notorious for furious outbursts of bad temper, which could last for hours before his equilibrium was restored.

Esher (a royal courtier who exercised great influence over military appointments) had dined with Smith-Dorrien (28 January 1908) to see if he was indeed "changed and weakened".

[35] However, following the sudden death of Sir James Grierson, he was placed in charge of the British Expeditionary Force II Corps, by Lord Kitchener, the new Secretary of State for War.

[35][37] Smith-Dorrien arrived at GHQ (20 August) and formally asked French's permission to keep a special diary to report privately to the King as His Majesty had requested.

Smith-Dorrien’s biographer AJ Smithers believes it more likely that he “bullied” Murray into issuing an order, and is highly critical of Sir John for failing to “grip” the situation.

[45] Because the German plan was to envelop the BEF from the west, most of their pressure fell on II Corps, which had already suffered higher casualties (2,000) in its fighting withdrawal on 24–25 August than at Mons the previous day (1,600).

[48] French had a long discussion with Murray and Wilson (25 August) as to whether the BEF should stand and fight at Le Cateau, a position which had been chosen for both I and II Corps to hold after they had retreated on either side of the Forest of Mormal.

II Corps had been harried by German forces as it retreated west of the forest and Sir John wanted to fall back as agreed with Joffre and hoped that the BEF could pull out of the fight altogether and refit behind the River Oise.

Allenby (GOC Cavalry Division) reached him at 2am on 26 August 1914, and reported that his horses and men were "pretty well played out", and unless they retreated under cover of darkness there would be no choice but to fight in the morning.

Hamilton (GOC 3rd Division) also reported that his men would be unable to get away before 9am, which also left little choice but to fight, lest isolated forces be overwhelmed piecemeal by the Germans.

Haig, despite believing French to be incompetent, wrote in his journal (4 September 1914) of Smith-Dorrien's "ill-considered decision" in electing to stand and fight at Le Cateau.

Murray later (in 1933) called Smith-Dorrien "a straight honourable gentleman, most lovable, kind and generous" but thought he "did wrong to fight other than a strong rearguard action".

However, the historian John Terraine praised Smith-Dorrien's decision, arguing that despite heavy casualties sustained by II Corps in the action, it materially slowed the German advance.

His writings from the time show that he was fully aware of the importance of artillery, machine guns and aircraft working in close cooperation with the infantry.

On 22 April 1915 the Germans used poison gas on the Western Front for the first time, and heavy casualties were sustained by the British and French troops.

On 27 April 1915, with a French counterattack to the north of the salient materializing later and on a smaller-scale than promised, Smith-Dorrien recommended withdrawal to the more defensible "GHQ Line".

On 30 April 1915, Haig wrote in his diary: After French refused permission to retreat, Smith-Dorrien noted (6 May 1915) that the planned counterattack was a complete failure with casualties higher than predicted by GHQ.

In 1914 French wrote that this had been written before he knew the full facts, and that Smith-Dorrien had risked destruction of his corps and lost 14,000 men and 80 guns (actual losses of each were around half of this number).

[66] On 3 September 1902 (on leave between being Adjutant General, India and taking command of 4th Division),[67] he married Olive Crofton Schneider (1881–1951) at St Peter's, Eaton Square, London, in a ceremony performed by his brother Rev.

[84][85] The following memorials have been established: Several places and institutions around the world have been named after Horace Smith-Dorrien, including: John Betjeman, mentions Horace in Chapter III "Highgate" of his autobiographical blank-verse poem Summoned by Bells: In late September, in the conker time, When Poperinghe and Zillebeke and Mons Boomed with five-nines, large sepia gravures Of French, Smith-Dorrien and Haig were given