Both of these had their ancestry in the catapults used centuries before by the Romans. The trebuchet was a giant catapult which threw a mass of rock from the end of a long revolving arm, the propelling power being provided by a counter-weight at the shorter end. The mangonel resembled a giant spoon and was operated by a windlass. It too could be used for hurling rocks and stones, as well as incendiary materials contained in pottery jars that burst on impact.

On the fourth night of the siege the Templars supported by the English made a spirited sortie from the northern gate of Acre, the Porte St Lazare, inflicting a number of casualties upon the enemy but failing to destroy the siege engines. A similar sortie a few nights later was made by the Hospitallers but proved no more successful. The disciplined Mameluke troops were waiting for them and the Hospitallers were forced to withdraw. But the main threat to the defences of Acre came not so much from the siege engines as from the large and efficient body of sappers and miners whom the Sultan had brought with him from Egypt. Day after day the Moslems were undermining the walls, concentrating especially on the strongholds of the protecting towers. The towers of England and of Blois and of St Nicholas were among the first to begin to crumble. Gradually under the continuing weight of the attack the defenders found themselves being forced back within the second ring of concentric walls.

At dawn on May 18th the Sultan launched a massive assault against the breached and ruined walls of this last Christian city in the Holy Land. As the siege engines continued to fire deep into the city, and as the air was darkened by a blizzard of arrows, the Mamelukes prepared for the general assault. Accompanying them, to inflame their ardour for battle as well as to demoralise the defenders, came no less than 300 camels with drummers continually thundering away on huge side-drums. The noise was indescribable and the weight of the attacking forces irresistible. By sunrise Moslem banners were fluttering along the walls and the advance columns were already overrunning the second line of defences and penetrating into the city. To the north the Templars were holding their own but the main Mameluke attack was thrown against the Hospitallers in the area of the Gate of St Antony. At this last moment—a moment which had to some extent arisen through the rivalry of the two Orders in the past—the Grand Master of the Templars led a supporting column down to give aid to the Hospitallers. This long area of wall against which was directed the main weight of the attack managed to hold out until well into the afternoon. Then it too was overrun and nearly all the Hospitallers were killed.

Meanwhile, to the south, where the English and French had been holding out against the Mameluke attacks, the evacuation of as many men, women and children as could be accommodated in the ships lying in harbour was already under way. There were not enough vessels, however, to remove anything like the total population of Acre and in the slaughter which later developed thousands were killed and more thousands dragged off to slavery. For the Order of St John that day marked the end of all their days in Outremer. Only a handful of them managed to escape, among them their Grand Master John de Villiers who had himself been seriously wounded in the fighting. The Templars, who had retreated into their great palace at the northern tip of the promontory, managed to hold out for over a week. But in the end the combined weight of the assaults and the continuous tunnelling activities of the besiegers brought down the walls of this, the strongest fortification in the city. The Grand Master of the Temple, Peter de Sevrey, together with some other knights had already been beheaded when they had gone out to try to negotiate a truce in order to save the lives of the women and children who had taken shelter with them. Now, as the battered walls of the palace collapsed, the last of the Templars in Acre along with many of the enemy were buried together in one great smoking ruin.

The whole city of Acre—its fortifications, walls, towers, merchant houses and store sheds, port installations and the warehouses that had harboured so rich a trade for centuries—was set afire and demolished. Within a few days such other few places as had remained within the Latin sphere were abandoned; the people fleeing by sea from such ancient cities as Beirut and Tyre, Haifa and Tortosa. Tyre, which in 332 B.C. had put up the best resistance of all the Phoenician cities to Alexander the Great, was the last to fall to the new conquerors. It was evacuated on July 14th, 1291. But whereas Alexander had brought Greek culture to the East, the Turkish Mamelukes brought nothing but fire and the sword. Baybers and those who followed him, including the now victorious Sultan Khalil, had finally achieved the dream of Saladin—the expulsion of the Franks.