A war fought on a narrow strip of land
Most crusading armies that reached the eastern Mediterranean fought in a small area: the Syrian and Palestinian coast, the cities just inland, and, from time to time, the Nile delta in Egypt. The land was crowded with walled towns and strong points, and the Muslim world around it was often divided among rival rulers. That division helps explain why the first crusaders succeeded and why later ones found things harder.
Antioch and Jerusalem, 1097 to 1099
The First Crusade crossed Anatolia and reached Syria in 1097. Its first great test was Antioch, a large city with long walls. The siege lasted months, and the crusaders were short of food. After the city fell in 1098, they were themselves besieged by a relief army and, according to the sources, won a battle outside the walls. Historians treat some of the dramatic details with caution, since the main accounts were written by participants or their admirers.
The army then moved south, and Jerusalem was taken in the summer of 1099 after a siege of several weeks. Siege towers and the weakness of the defenders, who were part of a Fatimid garrison, are commonly cited as factors. The capture was followed by a massacre of many of the inhabitants, an event remembered bitterly in the Islamic world and not disputed in broad outline.
Holding what was won
Most of the crusaders went home. Those who stayed carved out principalities, which became the Crusader States, along the coast and at Edessa, Antioch, Tripoli and Jerusalem. The Kingdom of Jerusalem was always short of fighting men. The settlers relied on coastal fortresses, on pilgrims and reinforcements arriving by sea, and increasingly on the Knights Templar and the Knights Hospitaller, who garrisoned castles and kept standing forces.
Edessa and the Second Crusade
In 1144 Zengi, the Muslim ruler of Mosul and Aleppo, captured Edessa. This shocked Western Europe and led to the Second Crusade in the late 1140s, led by the kings of France and Germany. The armies suffered losses crossing Anatolia, and the expedition ended with a failed attack on Damascus in 1148. It is usually counted as a failure. The episode also shows a pattern: crusaders arrived with large hopes but little local knowledge.
Saladin and the loss of Jerusalem
Over the following decades, Muslim Syria and Egypt were brought under a single ruler, Sultan Saladin. Once he controlled both, the crusader states were pressed from two sides. In 1187 his army met the Frankish field army at the Battle of Hattin, and it was destroyed, partly because it marched across dry country in summer. Jerusalem surrendered soon after. Saladin’s reputation for restraint in the aftermath is generally praised in both Muslim and Christian sources, though he was also a hard-nosed ruler who fought a long war.
The Third Crusade
The Third Crusade began in 1189. The German emperor Frederick Barbarossa drowned on the way in 1190, and much of his army turned back. The kings of France and England arrived by sea and joined the long siege of Acre, which fell in 1191. Philip of France went home soon after. Richard the Lionheart stayed, won a battle at Arsuf, and moved close to Jerusalem twice without attacking it, probably judging that it could not be held. The campaign ended in 1192 with a truce that left the crusaders a coastal strip and gave Christian pilgrims access to Jerusalem.
Egypt as the target
Later expeditions often aimed at Egypt, on the reasoning that it was the base of Muslim power. The Fifth Crusade took Damietta in 1219 but was forced to give it up in 1221 after an advance up the Nile failed during the flood season. Louis IX of France captured Damietta in 1249, and his army was defeated at Mansurah. He was captured and ransomed in 1250. In between, Emperor Frederick II recovered Jerusalem by treaty in 1229, with little fighting, though the city was lost again in 1244.
The end of the mainland states
From the mid-thirteenth century the Mamluk rulers of Egypt, who were former slave soldiers, took the offensive. They captured the remaining crusader strongholds one by one. The siege of Acre in 1291 ended the Latin presence on the mainland, and the survivors fell back to Cyprus. Crusading talk continued for generations afterward, but there was never again a Christian state of this kind on the Syrian coast.
Why the pattern repeated
A few ideas recur across the campaigns. Armies that moved quickly and lived off a divided opponent did well, and armies that were unprepared for heat, water shortage and long supply lines did badly. Sea power mattered, because the coast could only be held while ships could bring men and food. Unity among the Muslim rulers was the biggest variable of all. When it was weak, the crusaders gained ground, and when it grew, they lost it.