Question: When was the 1st Earl of Ypres born who attacked attacked the Boer force from the rear while mounted infantry?

Context paragraphs:
14th Light Horse Regiment (Australia): The 14th Light Horse Regiment was a mounted infantry or light horse unit of the Australian Army.  The unit takes its lineage from units raised as part of the colonial forces of the state of Queensland in 1860 and served during the Second Boer War and World War I.  In 1930 it was amalgamated with the 2nd Light Horse Regiment to become the 2nd/14th Light Horse Regiment (Queensland Mounted Infantry), a unit that continues to exist as part of the Australian Army today.

Australian Light Horse: Australian Light Horse were mounted troops with characteristics of both cavalry and mounted infantry, who served in the Second Boer War and World War I.  During the inter-war years, a number of regiments were raised as part of Australia's part-time military force.  These units were gradually mechanised either before or during World War II, although only a small number undertook operational service during the war.  A number of Australian light horse units are still in existence today, including the 2nd/14th Light Horse Regiment (Queensland Mounted Infantry), now an armoured reconnaissance unit equipped primarily with the ASLAV armoured fighting vehicle.

Battle of Beersheba (1917): The Battle of Beersheba (Turkish: "Birüssebi Muharebesi" , ), was fought on 31 October 1917, when the Egyptian Expeditionary Force (EEF) attacked and captured the Yildirim Army Group garrison at Beersheba, beginning the Southern Palestine Offensive of the Sinai and Palestine campaign of World War I.  After successful limited attacks in the morning, by infantry from the 60th (London) and the 74th (Yeomanry) Divisions of the XX Corps from the south-west, the Anzac Mounted Division (Desert Mounted Corps) launched a series of attacks.  These attacks, against the strong defences which dominated the eastern side of Beersheba, eventually resulted in their capture during the late afternoon.  Shortly afterwards, the Australian Mounted Division's 4th and 12th Light Horse Regiments (4th Light Horse Brigade) conducted a mounted infantry charge with bayonets in their hands, their only weapon for mounted attack, as their rifles were slung across their backs.  While part of the two regiments dismounted to attack entrenchments on Tel es Saba defending Beersheba, the remainder of the light horsemen continued their charge into the town, capturing the place and part of the garrison as it was withdrawing.

Battle of Poplar Grove: Battle of Poplar Grove.  was an incident on 7 March 1900 during the Second Boer War in South Africa.  It followed on from the Relief of Kimberley as the British Army moved to take the Boer capital of Bloemfontein.  The Boers were demoralised following the surrender of Piet Cronjé at the Battle of Paardeberg.  General Sir John French's cavalry attacked the Boer force from the rear while mounted infantry and horse artillery attacked from the right flank.  The Boers abandoned their positions in panic before the cavalry.  The commander-in-chief of the Free State forces, Christiaan de Wet, in his book called the chapter on the subject "Wild Flight from Poplar Grove".

John French, 1st Earl of Ypres: Field Marshal John Denton Pinkstone French, 1st Earl of Ypres (28 September 1852 – 22 May 1925), known as Sir John French from 1901 to 1916, and as The Viscount French between 1916 and 1922, was a senior British Army officer.  Born in Kent to an Anglo-Irish family, he saw brief service as a midshipman in the Royal Navy, before becoming a cavalry officer.  He achieved rapid promotion and distinguished himself on the Gordon Relief Expedition.  French had a considerable reputation as a womaniser throughout his life and his career nearly ended when he was cited in the divorce of a brother officer whilst in India in the early 1890s.

Queensland Citizen Bushmen: The Queensland Citizen Bushmen, also known as the 3rd Queensland Mounted Infantry, was a mounted infantry regiment raised in Queensland for service during the Second Boer War.  Formed as part of the third Queensland contingent with an original strength of 316 men, it departed for South Africa on 2 March 1900 aboard the "Duke of Portland".  Under the command of Major Walter Tunbridge, it initially served in Rhodesia, and later in west Transvaal, where it took part in the Relief of Mafeking, and actions at Koster River and Elands River.  It then served in northern Transvaal, including actions at Rhenoster Kop and Wolwekuil, and the advance on Pietersburg.  Fatal casualties included three men killed or died of wounds, and five dead from disease.  The unit returned to Australia in June 1901 on the "Morayshire".

1st Battalion, Canadian Mounted Rifles, CEF: The 1st Battalion, Canadian Mounted Rifles, CEF, was an infantry unit of the Canadian Expeditionary Force in the First World War.  Originally a mounted infantry unit named the 1st Regiment, Canadian Mounted Rifles, CEF, it was formed on November 7, 1914, in Brandon, Manitoba.  Part of the 1st Brigade Canadian Mounted Rifles, the unit landed in France on September 22, 1915, where the conditions of the Western Front made its mounts more of a hindrance than a benefit.

First Battle of Gaza: The First Battle of Gaza was fought on 26 March 1917, during the first attempt by the Egyptian Expeditionary Force (EEF) to invade the south of Palestine in the Ottoman Empire during the Sinai and Palestine Campaign of the First World War.  Fighting took place in and around the town of Gaza on the Mediterranean coast when infantry and mounted infantry from the Desert Column, a component of the Eastern Force, attacked the town.  Late in the afternoon, on the verge of capturing Gaza, the Desert Column was withdrawn due to concerns about the approaching darkness and large Ottoman reinforcements.  This British defeat was followed a few weeks later by the even more emphatic defeat of the Eastern Force at the Second Battle of Gaza in April 1917.

Victor Sellheim: Major General Victor Sellheim {'1': ", '2': ", '3': ", '4': "} (4 May 1866 – 25 January 1928) was an Australian military officer during the Second Boer War and World War I.  Sellheim fought in the Second Boer War with Chauvel's Mounted Infantry and fought in the Battle of Modder River.  For his actions during the war, Sellheim became a Companion of the Order of the Bath.  After serving in a variety of staff positions, he became Quartermaster general of the Australian Military Forces in 1912 and two years later was Adjutant general.  Between 1914 and 1916 he oversaw the Australian Imperial Force base at Cairo.  He became the Adjutant general again.  After the end of World War I, Sellheim became Quartermaster general in 1920 but resigned in 1927 to become Administrator of Norfolk Island, where he died on heart failure in 1928.

9th Virginia Regiment: The 9th Virginia Regiment was authorized in the Virginia State Troops on January 11, 1776.  It was subsequently organized between February 5 and March 16, 1776, and comprised seven companies of troops from easternmost Virginia.  The unit was adopted into the Continental Army on May 31, 1776.  The regiment participated in the Battle of Brandywine and the Battle of Germantown.  At Germantown, under the command of Colonel George Mathews, the unit became separated from the remainder of General Nathanael Greene's division and over 400 men were taken prisoner by the British.  The regiment penetrated so deeply into the British lines that it was isolated.  Four retreating companies of the 1st British Light Infantry Battalion found themselves in the rear of the Virginians and attacked.  Surprised, the 9th was driven farther into the British camp where it was beset by the brigade of Charles Grey, 1st Earl Grey and the 2nd British Light Infantry Battalion.  After being attacked on all sides and Mathews wounded, the regiment surrendered near Kelly's Hill together with part of the 6th Virginia Regiment.  The unit was consolidated with the 1st Virginia Regiment on May 12, 1779, and the consolidated unit was designated as the 1st Virginia Regiment.  The unit was captured on May 12, 1780, by the British Army at the Siege of Charleston and was disbanded on November 15, 1783.

Supporting paragraphs: Battle of Poplar Grove John French, 1st Earl of Ypres
Answer: 28 September 1852