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
The Northern Crusades or Baltic Crusades were religious wars undertaken by Catholic Christian military orders and kingdoms, primarily against the pagan Baltic, Finnic and West Slavic peoples around the southern and eastern shores of the Baltic Sea, and to a lesser extent also against Orthodox Christian Slavs (East Slavs). The crusades took place mostly in the 12th and 13th centuries and resulted in the subjugation and forced baptism of indigenous peoples.