Prisoner of war
A prisoner of war (POW, PoW, PW, P/W, WP, PsW, enemy prisoner of war (EPW) or "missing-captured") is a person, whether combatant or non-combatant, who is held in custody by a belligerent power during or immediately after an armed conflict. The earliest recorded usage of the phrase "prisoner of war" dates to 1660.
Belligerents hold prisoners of war in custody for a range of legitimate and illegitimate reasons, such as isolating them from enemy combatants still in the field (releasing and repatriating them in an orderly manner after hostilities), demonstrating military victory, punishing them, prosecuting them for war crimes, exploiting them for their labor, recruiting or even conscripting them as their own combatants, collecting military and political intelligence from them, or indoctrinating them in new political or religious beliefs.
Ancient times
For most of human history, depending on the culture of the victors, enemy combatants on the losing side in a battle who had surrendered and been taken as a prisoner of war could expect to be either slaughtered or enslaved. The first Roman gladiators were prisoners of war and were named according to their ethnic roots such as Samnite, Thracian, and the Gaul (Gallus). Homer's Iliad describes Greek and Trojan soldiers offering rewards of wealth to opposing forces who have defeated them on the battlefield in exchange for mercy, but their offers are not always accepted; see Lycaon for example.