After the Third Crusade, the re-established Crusader States managed to survive and even expand in power for the next several decades. Syria and Egypt were split between Saladin’s heirs, and the crusader kingdoms often enjoyed good relations with Ayyubid Egypt. Indeed, in 1229, a truce worked out between Holy Roman Emperor Frederick II and the Egyptian sultan al-Kamil resulted in the city of Jerusalem returning to Christian rule.
In the 1240s, forces far from the Levant brought down the Kingdom of Jerusalem. As the Mongols gradually conquered Central Asia, the Khwarazmian Turks were driven from their realm in the steppes into Syria and northern Iraq. They ended up allying with Ayyubid Egypt against the Crusader Kingdom of Jerusalem. In 1244, the combined armies of Damascus and Jerusalem were defeated by an Egyptian/Khwarazmian army. Jerusalem fell under Muslim rule, where it would remain until 1917.
In response to the fall of Jerusalem, Pope Innocent IV (r. 1243 – 1254) called a crusade that would be led by King Louis IX. While it had contingents from other Western European kingdoms, this effort was primarily from the French crown. Although King Louis IX was able to manage the impressive logistical feat of organizing and equipping an army that seized the northern Egyptian port of Damietta, the effort to take all of Egypt was ultimately unsuccessful. Over the course of 1250, the French army was surrounded in the swamps of the Nile Delta outside of Cairo and forced to surrender, with Louis being captured. The only lasting result: during the fighting, the Ayyubid sultan’s Mamluks launched a coup d’état and seized power in Egypt, thereby creating in Egypt a military power that would dominate the Levant for nearly three centuries.
In the four decades after Louis’s failure in the Nile Delta, the Mamluk sultans of Egypt would eventually conquer all of the Crusader States, with the last crusader stronghold in the Levant, the city of Acre, falling in 1291. Although Popes would still call crusades for military efforts against Muslim forces (and indeed, still make calls to retake the city of Jerusalem), crusading had failed. One reason for crusading’s ultimate failure was that, as Western European kings consolidated their power, they often had priorities other than crusading. For example, England’s Edward I spent a few months fighting in the Levant in 1271. However, he spent most of his reign fighting to subdue England’s neighboring kingdoms of Wales and Scotland.
In the end, the Crusades failed, and their greatest long-term impacts were the destruction of the Byzantine Empire and the growth of the sea power of Genoa and Venice, whose ships and sailors had transported people and supplies between Europe and the Crusader States.