Task: Question Generation
Input (English): Passage: Following the Mamluk victory over the Mongols in 1260 at the Battle of Ain Jalut by Qutuz and his general Baibars, Qutuz was assassinated, leaving Baibars to claim the sultanate for himself. As Sultan, Baibars proceeded to attack the Christian crusaders at Arsuf, Athlith, Haifa, Safad, Jaffa, Ascalon, and Caesarea. As the Crusader fortress cities fell one by one, the Christians sought help from Europe, but assistance was slow in coming. In 1268 Baibars captured Antioch, thereby destroying the last remnant of the Principality of Antioch, securing the Mamluk northern front and threatening the small Crusader County of Tripoli. Louis IX of France, having already organized a large crusader army with the intent of attacking Egypt, was diverted instead to Tunis, where Louis himself died in 1270. Prince Edward of England arrived in Tunis too late to contribute to the remainder of the crusade in Tunis. Instead, he continued on his way to the Holy Land to assist Bohemund VI, Prince of Antioch and Count of Tripoli, against the Mamluk threat to Tripoli and the remnant of the Kingdom of Jerusalem. On May 9, 1271, Edward finally arrived at Acre. He brought a small but not insignificant contingent of no more than 1,000 men, including 225 knights.
Output (English): How many fortress cities were attacked by Baibars?