Cavalié Mercer Alexander Cavalié Mercer ( 28 March 1783 – 9 November 1868 ) was a British artillery officer . Although he rose to the rank of general , his fame is as commander of G Troop Royal Horse Artillery in the thick of the fighting at the Battle of Waterloo , and as author of " Journal of the Waterloo Campaign " . Mercer ' s six - gun horse artillery troop arrived too late for the Battle of Quatre Bras , but it fought with the cavalry rearguard covering the army ' s retreat to Waterloo . The troop fought on the extreme right wing of Wellington ' s army at Waterloo , before being moved into the thick of the fighting nearer the centre of the line . There it beat off repeated charges by French heavy cavalry , disobeying orders to abandon the guns and retire inside nearby infantry square s as the enemy closed . The location of this action is marked by a memorial on the Waterloo battlefield . After the battle , Mercer ' s troop marched on Paris with the Allied armies , and formed part of the army of occupation . Mercer ' s " Journal " is an important source for historians of the Waterloo campaign , as well as a detailed description of the landscape and people of Belgium and France in the early 19th century . It is one of the few accounts of the period written by an artillery officer . Mercer remained in the peacetime army , twice serving in Canada . He was a painter of some merit , and a number of his watercolours of Canadian landscapes were purchased by the National Gallery of Canada in the 1980s . Before 1815 . Mercer was born in 1783 at Kingston - upon - Hull , Yorkshire , into a military family : his father was General Alexander Mercer of the Royal Engineers . He went to the Military Academy at Woolwich and was commissioned as a lieutenant in the Royal Regiment of Artillery in 1799 at the age of 16 . He served in Ireland in the aftermath of the Irish Rebellion of 1798 . He was promoted to second captain ( a rank unique to the Ordnance ) in 1806 . Promotion in the Royal Artillery was very slow , especially in peacetime , as it relied solely on seniority . Unlike in the rest of the British Army of the time there was no opportunity for purchase of commissions in the Ordnance . Mercer was not breveted as a major until 1 March 1824 , though this was then backdated to 12 August 1819 . Mercer was posted to G Troop Royal Horse Artillery around 1806 and joined Whitelocke ' s ill - fated Buenos Aires expedition in 1807 . He did not serve in the Peninsular War and next saw war service in the Waterloo Campaign . G Troop . In 1815 Mercer was acting commander of what was officially G ( Dickson ' s ) Troop , Royal Horse Artillery , but is usually referred to as Mercer ' s Troop or Mercer ' s Battery . Its modern successor is G Parachute Battery ( Mercer ' s Troop ) Royal Horse Artillery , part of 7th Parachute Regiment Royal Horse Artillery , which currently serves in the field artillery role with 16 Air Assault Brigade , and is equipped with the L118 Light Gun . G Troop served on the 1807 Buenos Aires expedition , but the G Troop of Waterloo was formed from the amalgamation of two other RHA troops before leaving Colchester for Belgium . It had the pick of the horses from each , and was therefore regarded as an exceptionally fine unit . When reviewing the cavalry at Grammont on 29 May 1815 , Blücher is supposed to have said " there is not one horse in this battery that is not fit for a field marshal " . The troop had five 9 - pounder guns ( which had recently replaced some of the RHA ' s 6 - pounders ) and a 5½ " howitzer , 80 gunners , 86 drivers and 226 horses . Waterloo Campaign . Mercer ' s Troop embarked for Belgium on 11 April 1815 , a few days after hearing of Napoleon ' s escape from Elba . From 1 May until the French invasion on 15 June it led a quiet life in the small village of Strijtem , west of Brussels . G Troop rode all day on 16 June , but arrived too late to participate in the Battle of Quatre Bras . It covered the retreat from Quatre Bras on 17 June , narrowly escaping capture by French cavalry . It was in action later the same day at Genappe with the cavalry rearguard . Arriving on the field of Waterloo , Mercer ' s Troop briefly took up a firing position on the famous knoll behind the sandpit , which would feature in the fighting the following day . Mercer was still acting as rearguard for Wellington ' s army , not realising that the entire army had halted on the ridge immediately behind him . His troop exchanged fire with arriving French batteries before retiring . After a miserable , hungry night in the mud and rain in the orchard of Mont St Jean farm , where Mercer is fabled to have drunk port from a chicken shaped goblet , Mercer found himself without orders in the opening phase of the battle , as d ' Erlon ' s infantry attacked Wellington ' s left . He was about to lead his troop into action on his own initiative when he was ordered to the extreme right of the line . That was a quiet sector , but in common with much of Wellington ' s artillery , Mercer disobeyed orders to refrain from counter - battery fire . He engaged enemy guns , attracting heavy fire from superior enemy artillery in return . In mid - afternoon Mercer ' s Troop was suddenly ordered into the hottest part of Wellingtons ' line , between the crossroads and Hougoumont , where its position is now marked by a memorial . It deployed immediately behind the ridge road , which was on a low embankment . The bank provided excellent cover from enemy artillery and increased the effectiveness of Mercer ' s case - shot . The troop was between two squares of Brunswick infantry , whom Mercer regarded as unsteady . He was ordered to lead his men into the squares as cavalry closed , but decided they would be safer at their guns . Unlike all the other batteries in the sector , the troop ' s gunners never abandoned their guns to take refuge in the infantry squares . Massed French heavy cavalry attacked repeatedly from about 3 . 15 pm . The Grenadiers à Cheval of the Imperial Guard were already emerging through the smoke at the trot as Mercer ' s guns deployed , so the troop opened fire with case - shot at close range , causing terrible casualties . The French hesitated , then the front ranks attempted to retreat as the rear ranks pushed forward , causing them to mill about under the execution of Mercer ' s guns before they eventually withdrew . Before the second charge of the heavy cavalry , Mercer ' s Troop was harassed by close - range carbine fire from mounted French skirmisher s , while Mercer held fire to conserve ammunition . To steady his men , Mercer promenaded across his troop ' s front on horseback , goading the enemy in French and attracting aimed but inaccurate carbine - fire in return . The second main attack came on in columns , led by cuirassier s . Mercer ' s Troop waited for them , double - loaded with case - shot over ball , and fired at 50 or 60 yards . Mercer reported that the whole front rank of the enemy went down , with the round - shot tearing through the column behind . The ground became virtually impassable with dead and wounded horses and men , so the enemy could not close the gun - line . Under the rapid fire of Mercer ' s Troop and the Brunswick infantry , the enemy fell like " grass before the mower ' s scythe " . The greatest danger to Mercer ' s men came between the charges , from French skirmishers and artillery . The third and final charge stood little chance of reaching the guns . On each occasion individual cavalrymen passed between the guns , but only so as to escape to the British rear . As the third attack withdrew , the troop had to cease firing to allow the Duke of Wellington to pass along the road . Shortly afterwards Wellington ' s infantry advanced , leaving the guns on the ridge to engage masses of French troops in the valley below . Towards the end of the action a battery established itself on the ridge to Mercer ' s left and fired into the flank of his troop , causing devastating casualties amongst the limber - horses . This battery was eventually driven off by fire from a newly arrived Belgian battery . The hostile battery may well have been Prussia n but Mercer did not believe it , despite being told so by a Brunswick cavalry officer . Due to its shortage of horses , the troop was unable to move when the general advance was ordered , and Mercer slept under a limber , amongst the dead and wounded . The troop had 5 killed and 15 wounded and lost 69 horses at Waterloo . It expended 700 rounds of ammunition . Sir Augustus Frazer said , " I could plainly distinguish the position of G Troop from the opposite height by the dark mass of dead French cavalry which , even at that distance , formed a remarkable feature on the field . " After Waterloo . Mercer ' s Troop stayed on the battlefield until 3 pm the following day , and Mercer spent the day touring the field , visiting Hougoumont and talking to the wounded . Once it had been rejoined by its ammunition and supply wagons , the troop moved off towards Nivelles , leaving some guns and carriages behind for lack of horses . It rejoined the Army near Mons on 21 June , and marched with it to the gates of Paris without seeing further action . It was ordered into cantonment s at Colombes early in July 1815 . Apart from two months of leave in England , Mercer spent much of the rest of the year enjoying tourist pursuits in Paris . Mercer was transferred to command D Troop RHA at Stains , also near Paris , in July 1815 and he returned with it to England in January 1816 . After the campaign Mercer was put on half - pay from 31 July 1816 until 1821 . Recalled to the peacetime army , he served twice in British North America , first as commander of the 6th company of the 5th battalion Royal Artillery at Quebec from 1823 . He was breveted major in 1824 , backdated to 1819 . He returned to England in 1829 and held commands at Woolwich and Devonport . He was promoted lieutenant - colonel on 5 June 1835 . He served again in British North America from 1837 to 1842 , commanding the artillery in Nova Scotia during the 1837 border dispute with the United States which became known as the Aroostook War . He was promoted to colonel on 2 April 1846 , to major - general on 20 June 1854 and to lieutenant - general on 29 August 1857 . He was commandant of the Dover garrison before he retired from active service , but he was appointed Colonel Commandant 9 Brigade Royal Artillery on 16 January 1859 , and as such he was never officially placed on the retired list . He was promoted to full general on 9 February 1865 . During his service in Lower Canada ( 1828 – 29 ) and Nova Scotia ( 1840 – 42 ) Mercer painted the watercolours which were acquired by the National Gallery of Canada in the 1980s . Mercer married Frances ( or Fanny ) Rice on 10 November 1813 at Bourton on the Water , Gloucestershire , while he was stationed in Woodbridge , Suffolk ; she travelled with him to France after his leave in November 1815 . They had one son , Cavalié A . Mercer , who edited the " Journal " after his father ' s death . Mercer and Fanny lived in Berkshire at the time of the Waterloo campaign , but in later life Mercer lived at Cowley Hill near Exeter . He died there on 9 November 1868 and is buried at St . David ' s Church , Exeter . His " Journal of the Waterloo Campaign kept throughout the campaign of 1815 " was published in 1870 , after his death . It was written some 30 years earlier , from the original notes Mercer wrote contemporaneously , with additions and verifications from correspondence and other sources . It covers the period from April 1815 to January 1816 , when Mercer returned to Canterbury with D Troop , with an interlude for his leave in England from September to November 1815 . By Mercer ' s own admission he had little time to write his journal in the hectic few days before and after Waterloo , so his account may not be entirely reliable . The " Journal " is notable for its lengthy descriptions of the countryside and its people , and especially of Parisian life under the Allied occupation . Very little of it is devoted to military matters , and indeed Mercer does not seem to have devoted much time to command , spending most of his days in country walks , riding or tourism in Paris .