along with all of his nephews and major associates, although many of his associates were spared. Emperor Wen became quickly known for his diligence in governing the state and his frugality, as well as his caring for the welfare of the people. He set up a system where officials, both at the capital and in provinces, were given relatively long office terms, but carefully monitored for their progress. He was particularly attentive to his brothers' ability to govern, offering them much advice while carefully fostering proper experience for them. One of them, Liu Yikang the Prince of Pengcheng, soon became known for his skills at governing Jing Province after replacing Xie, and in 428, Wang Hong, who was fearful of drawing attacks for having been prime minister for too long, offered to resign and give his authority to Liu Yikang. Emperor Wen declined at this point, but did transfer most of Wang Hong's authorities to Liu Yikang in 429. Also in 429, Emperor Wen created his oldest son by Empress Yuan, Liu Shao, crown prince. That year, Emperor Wen's maternal grandmother Lady Su died, and he mourned her greatly, wanting to posthumously create her titles, but because of opposition by the key official Yin Jingren (), he did not do so. Around this time, Emperor Wen also started preparing for a campaign against rival Northern Wei, seeking to recover several provinces lost to Northern Wei during the reign of Emperor Shao. In spring 430, he put Dao Yanzhi in command of a 50,000-man army to attack Northern Wei. Emperor Taiwu of Northern Wei, when informed by Emperor Wen's messengers that all Emperor Wen was interested in was to recover the provinces south of the Yellow River, retorted angrily that he would withdraw but return in the winter once the Yellow River froze, and that was what he initially did—withdrawing his armies south of the Yellow River to areas north, allowing Liu Song to recover the four key cities of Luoyang, Hulao, Huatai (滑台, in modern Anyang, Hunan), and Qiao'ao (碻磝, in modern Liaocheng, Shandong) without a fight. Instead of advancing further north into Northern Wei proper, however, Emperor Wen stopped and placed his troops along the Yellow River, even though he had entered into an alliance with Xia's emperor Helian Ding to conquer and divide Northern Wei. With Emperor Wen's forces immobile, Northern Wei was able to attack Helian Ding