I'm puzzled. How was a war to take Jerusalem a defence of Christian lands? I thought that Israel was always the land of the Jews?
Alternative history sources maintain that though the crusaders were Christian, many(if not all) were of the royal Jewish bloodline and entitled to rule these lands.
Obviously, it was the land where Jesus lived and died. At the time of the Crusades, there were many Christians living there alongside the Jews, but ALL were under the rule of the Muslims.
Actually, Palestine (by your leave, that was the name of the Roman province) was largely depopulated of Jews following the Roman seige and destruction of Jerusalem in 70 A.D.
After the seige, Jerusalem was such a minor city, that despite its first bishop, St. James, having presided at the Apostolic Council recorded in Acts, for centuries the see was suffregan to the Bishop of Caesarea. (Precedence of episcopal sees within the Empire was based on the importance of the city.) It was the Christian East Romans who rebuilt the city, gracing it with churches commemorating the sites of events in Our Lord's Passion--eventually granting its bishop the dignity of patriarch, despite having only a tiny flock compared to the other four patriarchates. And it, and all surrounding provinces were Christian lands by the time of the rise of Islam and the Crusades by virtue of having majority Christian populations and being part of the largest Christian nation--the Roman Empire (the Western scholarly renaming as 'Byzantine Empire' has no basis in fact, and is a matter of prejudice by those who either want to claim the mantle of Rome for the Papacy (or the Frankish Empire) or detach what they regard as the glories of pagan Rome from its long Christian history (as Gibbon who bizarrely named the retirment of the last Western Augustus to a villa near Naples in 476, 'the Fall of Rome' for polemical reasons).)