Third Crusade (1189-1192)
Upon hearing of the defeat at the Battle of Hattin, a new call for help was sent. By March 1188, Henry II of England, Richard (Henry's son), Philip II of France, and the Holy Roman Emperor Frederick I had sworn crusade vows. The French and English contingents were delayed in their departure by mutual suspicion. The Germany army was not delayed, but their progress disintegrated upon the death of Frederick I while crossing the Goksu river in June 1190. Henry II had died before even leaving on crusade, but Richard and Philip arrived in the Holy Land by the summer of 1191. They laid siege to Acre, which surrendered in July of that year. The two then worked out a compromise for who should control Jerusalem between the feuding parties from the dispute after Baldwin V's death.
Philip then returned to the west, leaving behind part of his army. Richard I, however, still tried to reclaim Jerusalem. To prevent delay, Richard killed the prisoners from Acre and went on to seize Arsuf and Jaffa and to refortify Ascalon. However, upon hearing of political turmoil at home, he made a treaty with Saladin (signed on September 2, 1192) and left to return to England on October 9, 1192. In 1193, Saladin died. While both Philip and Richard claimed to want to return, neither did. But in spring 1197, the Holy Roman Emperor Henry VI (son of Frederick I) mounted another campaign. This also ended in a truce on July 1, 1198 after Henry VI's death on September 28, 1197.
Fourth Crusade (1202-1204)
In 1198, Pope Innocent II called for another crusade, and in November 1199 a group of French knights took crusade vows. A treaty was made with the doge of Venice, Enrico Dandolo (who had been blinded in a pogrom against Latins in Constantinople) for aid in reaching the mideast. In 1202, when it became clear that they had fewer crusaders (and less money) than expected, some of the European forces seized the port of Zara from the king of Hungary, who was also under crusade vows, to earn their passage. In response Innocent III excommunicated the Venetians and forbade an attack on Byzantium This message did not arrive until too late, though whether or not it would not have made a difference is debatable.
The crusaders captured Constantinople in 1203 and put Alexius IV on the throne. In late January 1204, Murzuphlus soon seized the throne and named himself Alexius V; he subsequently ordered the crusaders to leave. The crusaders responded by retaking Constantinople, this time plundering it as well. They then founded the Latin Empire out of territory conquered from Byzantium. Byzantines formed a government in exile and managed to retake Asia Minor by 1235. In 1261 they recaptured Constantinople, ending the Latin Empire. The fighting, however, further weakened the Byzantine Empire, and in 1453, the Ottoman Turks took over region, capturing Constantinople on May 29, 1453.