Final answer:
Richard the Lionheart responded to the attack on 7 September 1191 as a leading figure in the Third Crusade, capturing Acre and later negotiating a treaty with Saladin that permitted Christian pilgrims to access Jerusalem.
Step-by-step explanation:
On 7th September 1191, Richard I of England, also known as Richard the Lionheart, was engaged in the Third Crusade. His response to the attack was part of the larger Christian military campaign in the Holy Land. After arriving at the last-standing Christian outposts, the crusaders managed to conquer the island of Cyprus and parts of the coastline but failed to advance further inland due to infighting and other challenges. Richard's leadership culminated in the capture of the city of Acre. The crusade did not recapture Jerusalem, but Richard negotiated a treaty with the Muslim leader Saladin that allowed Christian pilgrims to visit Jerusalem freely, leaving the city under Muslim control. This treaty represented a compromised success amidst the broader struggles of the crusade.