Final answer:
The Third Crusade was initiated in response to the Muslim capture of Jerusalem in 1187, leading to a Christian military campaign aimed at reclaiming the city. The efforts involved significant Christian leaders and resulted in a treaty that allowed pilgrim access to Jerusalem without altering its control. Subsequent crusades continued to reflect the tension and struggle between Christian and Muslim forces over the Holy Land.
Step-by-step explanation:
The Third Crusade was caused by the capture of Jerusalem in 1187 by the Muslim forces under Saladin. This event spurred a massive response from Christian Europe, with leaders like Richard the Lionhearted of England and others coming together, motivated by religious zeal, to recover the holy city for Christendom. The crusaders were initially successful in some areas, regaining control over the coastline of the Holy Land and the island of Cyprus, but internal conflicts and inability to move further inland led to the conclusion of the Crusade with a treaty that allowed Christian pilgrims access to Jerusalem, though it remained under Muslim control.
Pope Innocent III's call for later crusades, such as the Fourth and Fifth, reflected ongoing attempts to reclaim the Holy Land and solidify Christian presence in the face of Muslim rule. These attempts often struggled with issues such as financial constraints and shifting political alliances, including the unexpected involvement of the Crusaders in the political affairs of the Byzantine Empire during the Fourth Crusade.