There was no “Fourth Battle of Jerusalem.” The famous event typically associated with this era is the Fourth Crusade (1202–1204), which was called to recapture the Holy Land but infamously never made it to Jerusalem. [1, 2, 3]

Instead of fighting the Ayyubid Sultanate in Egypt/Palestine, the Crusaders made a fateful detour. Plagued by a lack of funds and swayed by Venetian political interests, they diverted to Constantinople—the capital of the Christian Byzantine Empire. In April 1204, the Crusaders besieged and viciously sacked the city, utterly destroying much of it and permanently weakening the Byzantine Empire. [1, 2, 3]

You can dive into the geopolitical derailment of this campaign through The Fourth Crusade – Wikipedia or explore how it was aimed at Jerusalem but hit Constantinople in TheCollector’s overview. For a wider public discussion on how the army never arrived at its target, you can browse through the Reddit community thread. [1, 2]

If you meant a different conflict in the Middle Ages or modern history, could you clarify which time period or who was fighting so I can find exactly what you are looking for?