Faaelin's immensely well-written timeline Prince of Peace has a Holy Roman Empire under Henry IV spreading all over Europe, also the Levant, Anatolia, and Egypt. Could any of these conquests have been possible in real life? This is how it went down in the timeline (very simplified):
Jersualem: (1197-1198) Henry attacks during the civil wars between Al-Adel and the rebels. The Battle of Ascalon proves to be crucial, shattering the Muslim resistance.
Constantinople: (1201) Phillip II Augustus (?) declares a crusade upon Byzantium on the behalf of Henry and invades with a vast fleet supplied by Pisa and Genoa and with troops from the HRE.
Egypt: Not exactly sure, to be honest.
Jersualem: (1197-1198) Henry attacks during the civil wars between Al-Adel and the rebels. The Battle of Ascalon proves to be crucial, shattering the Muslim resistance.
Constantinople: (1201) Phillip II Augustus (?) declares a crusade upon Byzantium on the behalf of Henry and invades with a vast fleet supplied by Pisa and Genoa and with troops from the HRE.
Egypt: Not exactly sure, to be honest.