Complex sentence: Vitellius marched on Italy at the head of the better part of the Rhine legions and defeated Otho's troops at the First Battle of Bedriacum, in which Otho himself was killed.
Split into simpler sentences: Vitellius marched on Italy at the head of the better part of the Rhine legions. He defeated Otho's troops at the First Battle of Bedriacum in which Otho himself was killed.