Final answer:
The successors of Frederick reached Acre in the Spring of 1191 during the Third Crusade.
Step-by-step explanation:
The individuals who continued the journey after Frederick's death reached Acre in the Spring of 1191. This event is a part of the Third Crusade, which took place between 1189 and 1192. The Third Crusade was led by several European monarchs, including Richard the Lionheart of England, with an aim to recapture Jerusalem and the Holy Land from Muslim forces under the leadership of Saladin. Despite internal conflicts and issues, they managed to secure the coast of the Holy Land and eventually negotiated a treaty that allowed Christian pilgrims to visit Jerusalem despite the city remaining under Muslim control.