Complex sentence: A steep decline in Byzantine-Venetian relations, following the Fourth Crusade, resulted in Byzantium favoring the Genoese in the conflict, who entered the war on the Genoan side.
Split into simpler sentences: A steep decline in Byzantine-Venetian relations, following the Fourth Crusade, resulted in Byzantium favoring the Genoese in the conflict. The Byzantines entered the war on the Genoan side.