In sum, the Crusaders, like the Tatars, are the enemies of the Muslims; and it is possible that the Crusaders of Acre would ally themselves with the Tatars, even though they dislike and feel afraid of the Tatars; and that the Crusaders are in their worst state of preparatory and spiritual weakness, although their city of Acre is still the most fortified in all territories of Palestine and Shaam.

In the light of those specifics, Qutuz, May Allaah have mercy upon him, found that fighting the Crusaders of Acre would have a negative impact on his army. It is true that the general and final goal of Qutuz, May Allaah have mercy upon him, was to liberate all the Muslim territories from any kind of occupation, be it Tatar or Crusader, but the aim of this particular stage should be to fight the Tatars. Without doubt, besieging the fortified city of Acre and fighting its garrison would weaken the Muslim army, waste its time, dissipate its powers and trouble the army before the great battle with the Tatars.
However, Qutuz, May Allaah have mercy upon him, at the same time, could not fight the Tatars in Palestine before he had settled the problem of the Crusaders in Acre. That is because any cooperation between the Tatars and the Crusaders would put the Muslim army between both horns of a dilemma: the Tatars on one side, and the Crusaders on the other side.

Hence, the best solution in the sight of Qutuz, May Allaah have mercy upon him, was to hasten to conclude a treaty with the Crusaders in Acre before allying themselves with the Tatars. Qutuz, May Allaah have mercy upon him, hastened to send an embassy to Acre to discuss a possible temporary armistice between the Muslims and the Crusaders. If the Muslim delegate succeeded, this would neutralize the Crusader army of Acre on the one hand, and secure the back of the Muslims on the other hand.

Actually, the Muslim delegate members discussed that armistice with the Crusader emirs, who were so much weak that they felt afraid if they did not gain a peace treaty from the Muslims, the latter would probably turn against them. That is why they accepted the idea of armistice quickly, and, moreover, some of them offered a proposal of military alliance to fight the Tatars. However, this idea was not approved by both parties. The remaining Crusaders feared leaving with their army from Acre, lest the Muslims would enter the city once they emerged victorious. Similarly, the Muslims did not feel safe from the possible betrayal of the Crusaders during the fight, given that the Tatars were cooperating with such Christian kings and emirs as the king of Armenia, the king of Georgia, and the emir of Antioch, and Kitbuqa, the Tatar leader at that time, was Christian.

http://300035.dotdothktrade.tech/en/artical/20796/neutralizing-crusader-army