Kammala wannan magana: A shekara ta 1355, bayan da Ottoman
Bayan kama Gallipoli a shekarar da ta gabata, Bulus ya shiga tattaunawa tare da sarkin Byzantine, John V Palaiologos, don sulhu tsakanin Byzantium da Cocin Katolika, don musayar taimakon soja na Yamma. Bulus ya samu amincewa mai yawa daga sarkin da ke cikin matsi, har da ƙarfafa Cocin Latin har ma da yaren Latin, aika ɗansa Manuel a matsayin ɗan garkuwa zuwa fadar papa, da kuma kafa wakilcin papa na dindindin a Constantinople. A lokacin zamansa a Constantinople, Bulus ya kuma sa hannu cikin jayayya ta tauhidi tsakanin Gregory Palamas da Nikephoros Gregoras. A farkon shekara ta 1356, Bulus, tare da jakadan Byzantine, "megas hetaireiarches" Nicholas Sideros, suka tashi zuwa fadar papa a Avignon, inda suka isa a farkon watan Yuni. Paparoma Innocent VI ya amsa tayin da sarki ya yi tare da cikakkun bayanai, kuma ya guji yin alƙawarin kansa ga aikawa da taimakon soja, amma ya aika da Peter Thomas da William Conti a matsayin jakadun papal zuwa Constantinople. Abubuwan fifiko da ra'ayoyi daban-daban na Byzantines da Latins sun ba da gudummawa ga lalacewa da kuma gazawar tattaunawar: wasiƙar 1357 ta John V ta kasance ba a amsa ta Innocent VI ba har zuwa mutuwarsa a 1362.