Complex sentence: In 1086 Tatikios was sent to Nicaea in an attempt to recapture it from the Seljuks; he was forced to retreat when he learned that Seljuk reinforcements were on their way.
Split into simpler sentences: In 1086 Tatikios was sent to Nicaea in an attempt to recapture it from the Seljuks. He was forced to retreat when he learned that Seljuk reinforcements were on their way.