 In preparation, Emperor Wen moved the troops stationed and supplies stored in the internal provinces to the boundary provinces.Meanwhile, however, before he could launch the campaign, Northern Wei's Emperor Taiwu invaded first in spring 450, putting Xuanhu (懸瓠, in modern Zhumadian, Henan) under siege for 42 days, and after much loss on both sides, Emperor Taiwu withdrew without having captured Xuanhu.This made Emperor Wen believe that Northern Wei's military power was waning, and he decided to launch his attack late in 450, despite oppositions by the generals Liu Kangzu (), who believed that the campaign should begin in spring 451, Shen Qingzhi (), who opined that Liu Song was not in shape to fight a war against Northern Wei, Xiao Sihua, and Crown Prince Shao.