Despite Liu Bobo's stated hatred for Northern Wei, he concentrated his efforts on undermining Later Qin, continually harassing Later Qin's northern territories and draining Later Qin's resources. He therefore did not settle in a capital city; rather, he roved about with his mobile cavalry, constantly looking for Later Qin cities to pillage. Also in 407, Liu Bobo sought marriage with a daughter of the
Southern Liang prince
Tufa Rutan, but Tufa Rutan refused. In anger, Liu Bobo launched a punitive raid against Southern Liang but then retreated. Tufa Rutan gave chase and —believing that he greatly outpowered Liu Bobo— was careless in his military actions. Liu Bobo led him into a canyon and then blocked the exit with ice and wagons, and then ambushed him—and the defeat was such that it was said that 60% to 70% of Southern Liang's famed officials and generals died in the battle. Tufa Rutan barely escaped capture. As a result, Tongwan became a highly defensible city, and the weapons and armors that he had were all of exceedingly high quality. Also in 413, Liu Bobo believed that his family name should be changed—since his ancestors took on the Liu family name from the
Han dynasty imperial house, believing that one of their female ancestors was a Han princess, but Liu Bobo believed this was improper. He therefore changed his family name to Helian—intending it to mean that his might was so great that it would, alas (赫 hè) be connected (連 lián) to the heavens. He also ordered the nobles to change their family name to Tiefa (鐵伐), intending it to mean that they were as strong as iron (鐵 tiě) and be able to attack (伐 fá) others. Thus, Helian was simply a Chinese folk etymology propagated by Helian himself as an explanation for his Xiongnu surname. In 414, Helian Bobo made his wife
Lady Liang "Heavenly Princess." (There is no further reference to the fate of his wife, Lady Mo, after he killed her father.) He made his son Helian Gui
crown prince, and made his other sons dukes. In 415, Helian Bobo entered into an alliance with
Juqu Mengxun, the prince of
Northern Liang. In 416, with Later Qin, now under the rule of Yao Xing's son
Yao Hong, under a major attack by the
Jin general
Liu Yu, Helian Bobo believed that Later Qin would fall to Jin, but that Jin would not be easily able to hold Later Qin's capital region —
Guanzhong. He therefore intensified his own attacks on Later Qin as well, and preparing to use the opportunity of Later Qin's destruction to seize more territory. As Later Qin neared destruction, Helian Bobo seized its western territory, centering Anding (in modern
Pingliang,
Gansu), and then prepared for an eventual confrontation with Jin forces, which destroyed Later Qin in 417 and captured its capital
Chang'an. The news of Later Qin's collapse reached Helian Bobo, who at once sent envoys to congratulate Liu Yu. Liu Yu, already aware of his reputation, soon dispatched an envoy in return. On learning that the envoy was coming, Helian Bobo resolved to put on a display. He ordered his officials to draft an ornate reply and then drilled himself on it until he could recite it from memory. When the envoy arrived, Bobo delivered the letter as if improvised, while scribes at his side wrote it down. The envoy brought the reply back, reporting that it had been dictated on the spot. Liu Yu, impressed, praised Bobo as a man accomplished in both letters and arms. In winter 417, Liu Yu, intent on wanting to seize the Jin throne, left Chang'an under the command of his 11-year-old son Liu Yizhen, and while he left several able generals to assist Liu Yizhen, those generals soon conflicted with and began killing each other—and eventually, Liu Yizhen, believing that the main assistant whom Liu Yu had left him, Wang Xiu, was about to rebel, had Wang executed. Meanwhile, Helian Bobo sent his crown prince Helian Gui, another son
Helian Chang, and Wang Maide to command armies south, not initially engaging Jin forces but isolating Chang'an from the rest of Jin territory—a task made easier when Liu Yizhen recalled Jin forces near Chang'an all to Chang'an. Upon hearing this, Liu Yu, sent his general Zhu Lingshi to replace Liu Yizhen and recalled Liu Yizhen, but as soon as Liu Yizhen and his troops left Chang'an, they were intercepted and crushed by Xia forces under Helian Gui. Liu Yizhen barely escaped, but the vast majority of the army was captured. Helian Bobo stacked the skulls of the Jin dead into a hill-like structure. Meanwhile, the people of Chang'an, who were angry that Liu Yizhen's forces pillaged the city before leaving, expelled Zhu, allowing Helian Bobo to enter Chang'an easily. Helian Bobo then claimed the title of emperor. In Chang'an, Helian Bobo invited the scholar Wei Zusi (韋祖思) of Chang'an to an audience. Frightened, Wei conducted himself with excessive caution and deference, which only angered Helian Bobo. Helian rebuked him: “In the past, when Yao Xing summoned you with the courtesies due a man of talent, you still dared to refuse to come. Now that I have brought you to my side, you cower as if before a demon. Do you truly take me for a demon? I am alive, and already you treat me this way. After I am dead, who knows what you will put to paper about me. I will kill you today and see how you malign me thereafter.” He then ordered Wei Zusi executed on the spot. == Late reign ==