The crusades were a series of religious wars fought over the control of what city?

Jerusalem  europeans will to trade with far east via for exemple the silk roade which was often closed by muslim rulers  were the economic factors that led to the crusades religious factor was will to retake jerusalm to be the sfae for piligrims once more political factor wa sinavsion fo seljuk turks on yzantium and emperoro alexios comnenos ask for