Driven back to Sardis, he witnessed the sacking of his city by the army of Cyrus the Great, in 546 b.c.
He returned to Sardis in order to witness the sacking of his city. 
mnli hypothesis: He returned to Sardis in order to witness the sacking of his city.  premise: Driven back to Sardis, he witnessed the sacking of his city by the army of Cyrus the Great, in 546 b.c.