(Mods feel free to remove this if it breaches the posting standards)
I'm asking because of the Battle of the Bastards (GOT S6E9) really had me wondering how there were suddenly walled heaps of corpses taller than a man on the battle field. Honestly, I had never seen it depicted before that episode. I tried to account for people falling during the initial contact, being trampled as the tides of men shifted, or the natural outcome of continuous volleys of arrows at specific ranges. I just wanted to know if that was a reality faced by the men of battle 600-2000 years ago.
It would be a highly exceptional situation, but it did happen, usually as the result of either a particularly tenacious defence or an attempted flight that ended up trapped by the terrain. I give you the Battle of the Long Walls of Corinth (392 BC):
When the Spartans saw that the forces opposed to the Sikyonians were victorious, they issued forth from the stockade and went to the rescue, keeping the stockade on their left. But when the Argives heard that the Spartans were in their rear, they turned around and burst out of the stockade again on the run. And those upon their extreme right were struck on their unprotected sides by the Spartans and killed, but those who were near the wall crowded together in a disorderly mass, continued their retreat towards the city. When, however, they came upon the Corinthian exiles and discovered that they were enemies, they turned back again.
Thereupon some of them, climbing up by the steps to the top of the wall, jumped down on the other side and were killed; others perished around the steps, being shoved and struck by the enemy, and still others were trodden under foot by one another and suffocated.
And the Spartans had no shortage of people to kill; for then at least the god granted them an achievement such as they could never even have prayed for. For to have a crowd of enemies delivered into their hands, frightened, panic-stricken, presenting their unprotected sides, no one rallying to his own defence, but all rendering all possible assistance toward their own destruction—how could anyone help seeing this as a divine gift? On that day, so many fell within a short time that men accustomed to seeing heaps of corn, wood, or stones, now saw heaps of dead bodies.
-- Xenophon, Hellenika 4.4.11-12