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.
Northern Crusades
Moving in the wake of German merchants who were now following the old trading routes of the Vikings, a monk named Meinhard landed at the mouth of the Daugava river in present-day Latvia in 1180 and was made bishop in 1186. Pope Celestine III proclaimed a crusade against the Baltic heathens in 1195, which was reiterated by Pope Innocent III and a crusading expedition led by Meinhard's successor, Bishop Berthold of Hanover, landed in Livonia (part of present-day Latvia, surrounding the Gulf of Riga) in 1198. Although the crusaders won their first battle, Bishop Berthold was mortally wounded and the crusaders were repulsed.