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.
Christianization
The Northern Crusades (or "Baltic Crusades") were crusades undertaken by the Catholic kings of Denmark and Sweden, the German Livonian and Teutonic military orders, and their allies against the pagan peoples of Northern Europe around the southern and eastern shores of the Baltic Sea. Swedish and German campaigns against Russian Eastern Orthodox Christians are also sometimes considered part of the Northern Crusades.
Some of these wars were called crusades during the Middle Ages, but others, including most of the Swedish ones, were first dubbed crusades by 19th-century romantic nationalist historians. Lithuania and Samogitia were ultimately Christianized from 1386 until 1417 by the initiative of the Grand Duke of Lithuania Jogaila and his cousin Vytautas.