Final answer:
Richard the Lionheart set sail from Acre during the Third Crusade, after the city was handed over to Christian forces in 1191, and subsequently negotiated a treaty for Christian pilgrim access to Jerusalem.
Step-by-step explanation:
Richard I of England, known as Richard the Lionheart, set sail from Acre during the Third Crusade. This was part of a series of campaigns undertaken by European Christians to reclaim the Holy Land from Muslim control.
The Third Crusade, spanning from 1189 to 1192, famously featured Richard I, as he was one of the key figures in commanding the Christian forces.
While there are various interpretations of specific timelines, it's generally accepted that Richard departed from Acre after arriving in the Holy Land and being involved in the successful siege and subsequent handover of the city, which ended on July 12, 1191.
Later, Richard negotiated with Saladin leading to the Treaty of Jaffa which allowed access to Jerusalem for Christian pilgrims. The Third Crusade is noted for both its military engagements and the chivalry of its leading figures.