Military history of the Crusader states
The Seljuk–Crusader War began when the First Crusade wrested territory from the Seljuk Turks during the Siege of Nicaea in 1097 and lasted until 1128 when Zengi became atabeg of Aleppo. At the latter date, the chief threat to the Crusaders from the east and north became the Zengids. The conflict was generally fought between European Crusaders and the Seljuk Turks and their vassals. The Muslim Syrian emirates occasionally allied themselves with the Christians against rival states.
Eighth Crusade
The Eighth Crusade was a crusade launched by Louis IX of France against the city of Tunis in 1270. The Eighth Crusade is sometimes counted as the Seventh, if the Fifth and Sixth Crusades of Frederick II are counted as a single crusade. The Ninth Crusade is sometimes also counted as part of the Eighth. The crusade is considered a failure after Louis died shortly after arriving on the shores of Tunisia, with his disease-ridden army dispersing back to Europe shortly afterwards.