The Siege of Damietta
The fifth Crusade took place from 1213 to 1221 CE. Frederick II of Germany promised to lead the Crusade but in the end he sent Louis I, Duke of Bavaria, instead. When the Crusaders first arrived in the Holy Land they came under the command of John of Brienne, King of Jerusalem.
Jerusalem itself was at this point under Egyptian control. The Crusaders' plan was to attack Egypt in order to force the Egyptians to hand over strategic areas in Palestine and even Jerusalem itself.
In early 1218 the Crusaders finally landed at Damietta and found themselves facing Malik al-Kamil, the son of the Sultan, with a army twice the size of the Crusaders.
The city of Damietta withstood the siege for one and a half years but finally fell in November 1219.