Complex sentence: Suleyman intercepted Botaneiates' small force between Cotyaeum and Nicaea, whereupon the usurper persuaded Suleyman to join his rebellion by offering him incentives superior to those of the emperor.
Split into simpler sentences: Suleyman intercepted Botaneiates' small force between Cotyaeum and Nicaea. Through inducements the usurper persuaded Suleyman to join his rebellion against the emperor.