What did pope urban 2 do to aid byzantine empire?

Pope Urban II played a crucial role in aiding the Byzantine Empire by launching the First Crusade in 1095. He responded to a plea for help from Byzantine Emperor AlexiOS I Komnenos, who sought military assistance against the Seljuk Turks threatening his territory. Urban's call to arms not only aimed to reclaim the Holy Land but also sought to reinforce Byzantine power by encouraging Western knights and soldiers to join the campaign, ultimately leading to the capture of Jerusalem in 1099. This alliance, though initially beneficial, also set the stage for complex relations between the Western and Eastern Christian churches.