Complex sentence: As the Persians retired south, Astyages readily abandoned the city partly on the scant sources from Nicolaus, therefore not becoming a complete victory for Astyages, as he is not known to put a garrison there after he and his forces went south after the Persians.
Split into simpler sentences: As the Persians retired south, Astyages readily abandoned the city, which is based on the scant sources from Nicolaus. Therefore not becoming a complete victory for Astyages, as he is not known to put a garrison there after he and his forces went south after the Persians.