The Sui army defeated the Yijishan and Yiaozhou defense lines, and Li Daliang was temporarily stunned. In Li Daliang's plan, with these two lines of defense, he could maintain a stalemate with the Sui army for a month or two anyway.
Li Daliang never thought that these two lines of defense would be defeated head-on in a short period of time. He had been worried that the Sui army would make a major detour