On August 20, 1191, Crusader King Richard I killed between 2500-3,000 Muslim prisoners in Ayyadieh. An excerpt from the article:
"The Massacre of Prisoners
An even more controversial episode than the question of whose flags to put where was Richard's treatment of the city's inhabitants. 2,500 prisoners (or perhaps 3,000, depending on sources), including women and children, were summarily executed on Richard's orders on 20 August 1191 CE. Other prisoners had already been exchanged between the two sides, including some nobles who could be profitably ransomed, but it seems that there was a delay of some kind, the relic of the True Cross was not returned as promised, and the English king was suspicious of the enemy's dithering as any delay meant Saladin could better prepare for the next confrontation as the Crusaders moved south. The bound prisoners were mercilessly cut down using swords, lances, and even stones. Although some of Saladin's remaining troops tried to intervene, they could not prevent the massacre. Saladin had been remarkably generous with his prisoners in the previous years, although he had had no qualms at all about executing any knights belonging to the military orders. The contrast in the treatment of civilian prisoners was a stark one, even if some have argued that Richard could not have allowed the men their freedom when he was just about to march southwards and so leave his army open to an attack from the rear if the prisoners had organised themselves into a fighting force.
Aftermath
Guy of Lusignan was made the new king of Cyprus, which had been sold by Richard to the Knights Templar to raise more cash for the Crusade. Unfortunately, Philip was obliged to return home in August 1191 CE due to political problems in Flanders which threatened his throne. Still, Acre was an excellent capture, and although many men and resources had been lost in its gain, the Crusader army was ready to march further south and take on the much bigger challenge of capturing Jerusalem. It seemed that the tide had turned and Acre was a morale-boosting victory, just as it was a damaging loss to Saladin, not perhaps in men or material but certainly to his carefully cultivated aura of invincibility.
As it turned out, the western army would be harassed continuously as it marched onwards. The two sides clashed again in September at the battle of Arsuf. Although a victory was gained against Saladin, the Crusaders were so depleted and the weather was so poor that a siege of the Holy City was abandoned. The task would have to be completed by calling the Fourth Crusade in 1202 CE which, in the event, again got side-tracked by prizes elsewhere and, instead of taking Jerusalem, attacked Constantinople in 1204 CE."