 Instead of advancing further north into Northern Wei proper, however, Emperor Wen stopped and placed his troops along the Yellow River, even though he had entered into an alliance with Xia's emperor Helian Ding to conquer and divide Northern Wei.With Emperor Wen's forces immobile, Northern Wei was able to attack Helian Ding and greatly damage Xia (eventually leading to its destruction in 431) absence.Afterwards, Northern Wei prepared to attack the south.