Complex sentence: In the course of their campaign the Byzantines seized Preslav and detained Boris II. Initially John I Tzimiskes presented himself as a liberator but Boris II was promptly forced to ritually abdicate in Constantinople.
Split into simpler sentences: In the course of their campaign the Byzantines seized Preslav and detained BorisII. Initially JohnI Tzimiskes presented himself as a liberator but BorisII was promptly forced to ritually abdicate in Constantinople.