The Battle of Waterloo left 40000 men and 10000 horses dead on the field. Between cavalry, dragoons, officer’s mounts, and draft animals, the armies of the day were heavily dependent on horses, and so the horses also became casualties. Among those present at the battle was Captain Alexander Cavalié Mercer of the Royal Horse Artillery. His company of guns and horses were in the thick of battle all day and took many losses. In his memoir, Journal of the Waterloo Campaign (1870), he writes movingly of one of these casualties.
A distressing circumstance connected with this (shall I confess it?) made even more impression on my spirits than the misfortune of Gunner Hunt. Bolton’s people had not been long engaged when we saw the men of the gun next to us unharness one of the horses and chase it away, wounded, I supposed; yet the beast stood and moved with firmness, going from one carriage to the other, whence I noticed he was always eagerly driven away. At last two or three gunners drove him before them to a considerable distance, and then returned to their guns. I took little notice of this at the time, and was surprised by an exclamation of horror from some of my people in the rear. A sickening sensation came over me, mixed with a deep feeling of pity, when within a few paces of me stood the poor horse in question, side by side with the leaders of one of our ammunition wagons, against which he pressed his panting sides, as though eager to identify himself as of their society—the driver, with horror depicted on every feature, endeavouring by words and gestures (for the kind-hearted lad could not strike) to drive from him so hideous a spectacle. A cannon-shot had completely carried away the lower part of the animal’s head, immediately below the eyes. Still he lived, and seemed fully conscious of all around, whilst his full, clear eye seemed to implore us not to chase him from his companions. I ordered the farrier (Price) to put him out of his misery, which, in a few minutes, he reported having accomplished, by running his sabre into the animal’s heart. Even he evinced feeling on this occasion. (vol I, pp. 304—305)
The incident clearly made a deep impression on Mercer and was vivid when he wrote his Journal decades later. And indeed, it still stands as a poignant reminder of the pain, suffering, and death inflicted by battle.