Liu Song launches a major attack in…

Liu Song launches a major attack in spring 430, and Emperor Taiwu, judging his own defenses south of the Yellow River to be unable to withstand a Liu Song attack, withdraws them north, judging correctly that Liu Song forces would stop at the Yellow River, planning to counterattack in the winter after the river freezes.

Meanwhile, Emperor Taiwu, hearing that Liu Song and Xia had subsequently entered into a treaty to attack him and divide Northern Wei lands, judges correctly that despite the treaty Liu Song has no intention of crossing the Yellow River north, and he decides to destroy Xia once and for all.

In fall 430, he makes a surprise attack on the new Xia capital Pingliang (in modern Pingliang), while Helian Ding is engaging Western Qin's prince Qifu Mumo, putting Pingliang under siege, but although he now sends Helian Chang to Pingliang to try to persuade its defender, Helian Shegan, younger brother to both Helian Chang and Helian Ding, to surrender, Pingliang will not fall quickly.

However, the Northern Wei general Tuxi Bi engages Helian Ding as Helian Ding is trying to relieve Pingliang, defeats him and surrounds him at the Chungu Plains (also in modern Pingliang).

Northern Wei forces surrounds him, and his army becomes hungry and thirsty.

After several days, he forcibly fights his way out of the siege, but his forces mostly collapse, and he himself is badly injured.

He gathers the remaining forces and flees to …