In December 1250, An-Nasir Yusuf attacked Egypt after hearing of al-Mu'azzam Turan-Shah's death and the ascension of Shajar al-Durr. An-Nasir Yusuf's army was much larger and better-equipped than that of the Egyptian army, consisting of the forces of Aleppo, Homs, Hama, and those of Saladin's only surviving sons, Nusrat ad-Din and Turan-Shah ibn Salah ad-Din. Nonetheless, it suffered a major defeat at the hands of Aybak's forces. An-Nasir Yusuf subsequently returned to Syria, which was slowly slipping out of his control.

The Mamluks forged an alliance with the Crusaders in March 1252 and agreed to jointly launch a campaign against an-Nasir Yusuf. King Louis, who had been released after al-Mu'azzam Turan-Shah's murder, led his army to Jaffa, while Aybak intended to send his forces to Gaza. Upon hearing of the alliance, an-Nasir Yusuf immediately dispatched a force to Tell al-Ajjul, just outside Gaza, in order to prevent the junction of the Mamluk and Crusader armies.;

Realizing that a war between them would greatly benefit the Crusaders, Aybak and an-Nasir Yusuf accepted Abbasid mediation via Najm ad-Din al-Badhirai. In April 1253, a treaty was signed whereby the Mamluks would retain control over all of Egypt and Palestine up to, but not including, Nablus, while an-Nasir Yusuf would be confirmed as the ruler of Muslim Syria. Thus, Ayyubid rule was officially ended in Egypt.