 Minister of War Bai Gui (白圭) had tried to implement an offensive solution since taking office in 1467, and he objected to Yu's proposal because of cost fears.On 20December 1472, amid reports of people fleeing the frontier provinces due to the harsh military levies imposed to finance offensive campaigns, Yu reasoned that his wall project would not be as costly as the offensive strategy, and that the wall would be a temporary measure that would allow the Ming to restore its military and economic strength.The court and emperor approved the plan, and the 1473 victory in the Battle of Red Salt Lake (紅鹽池) by Wang Yue (王越) deterred Mongol invasions long enough for Yu Zijun to complete his wall project in 1474.