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.
The Politically Incorrect Guide to Islam (And the Crusades)
Spencer claims Islam as militant and oppressive, and argues that the Crusades were a late response of European civilization to centuries of invasion and occupation which had begun at the turn of the 8th century in the Iberian Peninsula, Italy, Sicily, France, and the majority of Eastern Europe. He attributes the perceived civilizational clash between Islam and the West in the 21st century to a continuation of a 14 century long jihad began at the inception of Islam and discusses the what he claims are difficulties of treating this topic in the current political climate.