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.
Crusade of 1197
The Crusade of 1197, also known as the Crusade of Henry VI () or the German Crusade ("Deutscher Kreuzzug") was a crusade launched by the Hohenstaufen emperor Henry VI in response to the aborted attempt of his father, Emperor Frederick Barbarossa during the Third Crusade in 1189–90. 
Thus the military campaign is also known as the "Emperor's Crusade" (echoing the name "Kings' Crusade" given to the Third Crusade).