Final Answer:
Isaac Angelus prevented Blocked the march through Anatolia, contrary to an agreement with Frederick.
Thus the correct option is (C).
Step-by-step explanation:
Isaac Angelus and Frederick Barbarossa, leaders of the Byzantine Empire and the Holy Roman Empire respectively, entered into an agreement during the Third Crusade. According to historical records, Frederick sought a safe passage through Anatolia to reach the Holy Land. However, Isaac Angelus reneged on the agreement by blocking the march through Anatolia, thus preventing the Holy Roman Emperor and his forces from advancing.
This breach of the agreement had significant consequences for the Third Crusade. The inability of Frederick Barbarossa's army to pass through Anatolia hindered the overall coordination and effectiveness of the Christian forces in the Holy Land. The Byzantine obstruction created a strategic setback for the Crusaders and altered the dynamics of the campaign against Saladin.
Isaac Angelus's decision to block the march through Anatolia added a layer of complexity to the already challenging political landscape of the Third Crusade. The failure to uphold the agreed-upon terms strained the alliance between the Byzantine Empire and the Holy Roman Empire, impacting the Crusaders' ability to mount a united front against the common adversary, Saladin.
Thus the correct option is (C).