Acre had long been the most important sea port, which was well fortified, built on a peninsula and protected by the sea, with walls dotted with twelve towers.
From 1191, was the headquarters of the Order of the Knights Hospitaller. A strong medieval force of Teutonic Knights and Knights Templar were also located in the sea-port.
On the 28th May 1291, the Order of the Knights Templar, surrendered their fortified city of Acre to the Mamlukes, which had been under constant siege.
The loss of Acre was more than a defeat, for it had been captured by Richard the Lionheart on the 12th July 1191, and become home to Templars and Hospitallers.
Losing Acre marked the end of an era, they had lost their headquarters in the east, and the Templar Grand Master; Theobaud Gaudin in battle. William de Beaujeu next elected Grand Master of the Knights Templar, from Sidon, the Templar Fortress some sixty miles north of Acre.
Beaujeu’s new Grand Master of the Order, left the island for Cyprus, and sought out assistance for his brethren. As much as he tried, no help came, and on the 12th July, they were forced to abandon Acre and join fellow comrades on Cyprus. On the 14th July, Christian forces left Acre by sea in the dead of night bound for Cyprus.
Pope Nicholas IV, with a heavy heart, heard of the Christian defeat at Acre, and sought a plan should be drawn up, to take back the Holy Land. Sadly, before anything could be put in place, Pope Nicholas IV died.