 Unable to breach the adamant fortress despite months of siege, Tang eventually staked everything on the construction of a huge mound, designed to tower over the walls of the fortress; however, the defenders captured and successfully held the mound despite three days of frantic assaults by Tang troops.Furthermore, exacerbated by worsened conditions for the Tang army due to cold weather (and winter approaching) and diminishing provisions, Emperor Taizong was compelled to order a withdrawal from Goguryeo on October 13, but left behind an extravagant gift for Yang Manchun, the commander of Ansi Fortress.Emperor Taizong attacked Goguryeo again in 647 and 648, but was unsuccessful.