The Seventh Crusade
Saint Louis
The Seventh Crusade was not started by any Pope, but by King Louis IX of France, who became known later as Saint Louis because of his great devotion to God. After the Mamluks took Jerusalem in 1244 AD, Louis announced his Crusade (in 1245). Louis raised money from church tithes and then sailed to Cyprus in 1248 (when he was 34 years old).
From Cyprus, Louis attacked and took the port of Damietta in Egypt, which had caused so much trouble in the Fifth Crusade. The Ayyubids were very weak now and could not stop him. Using Damietta as a base, Louis then attacked Cairo, but the Mamluks arrived and defeated him. Louis was taken prisoner, and to get him back the French had to pay a lot of gold and give Damietta back.

The Fortress of Acre
Louis and his army left for Acre (AH-ker) in Syria. In Acre, he tried to negotiate with the Mongols to get their help against the Mamluks, but the Mongols weren't interested. By 1254, Louis (now forty years old) had run out of money. Also, his mother, Blanche of Castile, died. She had been ruling France while Louis was away, and with her dead Louis had to go home and take charge.