The Xiongnu sent an envoy, Wen Hebo Lubu.

  Lü Bu then took in Cai Yan and her family, settling them in a residence near the government office of Beidi Commandery. Although he assigned some soldiers from Beidi to guard them, it was actually for their protection. Lü Bu often brought his wives, Lady Yan and Lady Li, to visit Cai Yan's family, frequently sending over gifts such as meat, furs, utensils, and other items. Cai Yan's family enjoyed the treatment of a "super prisoner".

  Lü Bu treated Cai Yong with multiple reasons. Firstly, Lü Bu was curious about Cai Yong's identity and respected him. Secondly, Cai Yong's musical skills were exceptional, which pleased Yan Ni who loved music. Moreover, although Lü Bu killed people like flies, he also had a brain and appreciated the few literati in the north. Fu Xuan was busy with government affairs and rarely had spare time except when discussing politics with Lü Bu. Jia Xu had his own concerns and wasn't one to pour out his heart. Gao Shun spoke little and spent most of his time with those orphaned soldiers. As for Yan Ni, whenever she had time with her, Lü Bu would rather play games with her in bed. Therefore, only Fu Xuan was someone who could have a decent conversation with Lü Bu. However, Fu Xuan had ambitions and took the relationship between the northern Di and Qiang tribes and the Han people very seriously, so he often went to inspect them, leaving little time for himself. The others were all warriors. Now that Cai Yong had arrived, Lü Bu naturally took good care of him, treating him as a friend rather than a prisoner.

  In the sixth month of the sixth year of Guanghe, the Xiongnu Chanyu sent an envoy to meet Lü Bu and requested that he send troops to join forces with him to attack the Left Virtuous King Chezhou and the Wusun tribe. Lü Bu was pleased when he saw that the Southern Xiongnu Chanyu had sent an envoy to see him, bringing with him a large quantity of furs and goods.

  Liu Bao was killed by Lü Bu, and although Zuo Xianyu and Wusi had annexed Liu Bao's forces, they were driven out of the Hexi Corridor by Lü Bu. The Chanyu Qiangqu then wanted to use Lü Bu's power to join forces and completely eliminate the Left Worthy King's forces. He sent an envoy to see Lü Bu, hoping to join forces with him to destroy the Left Worthy King's forces and divide their land and tribes.

  At this time, Lü Bu was in a predicament with no place to plunder. The imperial court also cut off military supplies. The Xiongnu envoy came to see him, which coincided with his intentions. He then spoke kindly to the Xiongnu envoy and expressed his willingness to join forces with the Xiongnu to attack Zuo Xianwang. After agreeing on a time for the joint attack, he sent the Xiongnu envoy away.

  Lü Bu plundered the nomadic tribes, gaining advantage after advantage, and his heart became greedy. Now that the Chanyu was seeking him out, although it was in line with his wishes, Lü Bu was still greedy and wanted to take advantage of this opportunity to gain more benefits. After sending off the Chanyu's envoy, he invited Jia Xu, Gao Shun, and others into the military camp to discuss matters. They discussed how to divide up the territory and subordinates of Zuo Xianwang.

  Although the Zuoxianwang Department was driven out of the Hexi Corridor by Lü Bu, its territory was still comparable to that of Beidi. The Zuoxianwang Department marched south into Wuwei Commandery, bordering on Fuping County in Beidi Prefecture to the north, and extending as far as Jiluozhai.

  Che Zhou, Wu Su and Liu Biao's forces combined had a population of over 100,000, with more than 10,000 to 20,000 skilled warriors. Moreover, the northern army needed to join forces with the Xiongnu Chanyu to attack Zuo Xianwang, which would require crossing the Yellow River. Although the Xiongnu forces also had around 200,000 to 300,000 soldiers, the northern army only had a little over 5,000 soldiers, so Lü Bu had to be cautious in his response.

  Lü Bu of the Xiongnu Left Wing had given up on the imperial court. The court still owed him a lot of military expenses, so Lü Bu didn't expect the court to provide assistance and could only rely on himself.

  In the military camp, Lü Bu informed his generals that he wanted to unite with Chanyu to destroy Left Worthy King. However, Beidi was weak and had a population of only over 500,000, which was less than half of Left Worthy King's population. The military strength was even weaker, with only over 5,000 soldiers, which was only one-third of Left Worthy King's forces. Therefore, they needed to be doubly cautious.

  Fu Xian saw the strength of both sides clearly and said, "Sir, you want to ally with Chanyu to rebel against Left Worthy King, this is a national plan, but...but now the court has no time to care about the northern region, we northerners have few soldiers, if one is not careful, all the hard work of this year will be lost. Does Governor Sir really want to unite with Chanyu?"

  Lü Bu said: "At this time, it is the time to solve the troubles of Zuo Xianwang's department and the great Han border counties. How can we give up at this time? This battle must be won."

  Fu Xuan said: "The adults are strong, the Southern Xiongnu are repeatedly unpredictable and often cause trouble in the left division. We should take this opportunity to forever eliminate future troubles."

  Lü Bu smiled and nodded at Fu Xi, but in his heart he sighed: Fighting a war is not like plundering. Plundering is slaughtering nomadic people, even if there are those who resist, they are only a few strong men. But really fighting against Zuo Xian Wang, that's soldier against soldier, knife against knife, bravery alone won't do. You also need strategy, tactics, equipment. If you don't win, your life is gone, and the northern lands will be finished too.

  Lü Bu instinctively looked at Jia Xu and asked: "Jia Xu, do you have any valuable opinions?"

  Jia Xu saw Lü Bu and asked him, busy raising his head to respond. Jia Xu didn't quite understand Lü Bu. If you say Lü Bu is a butcher, then he kills the barbarians without mercy, leaving no one alive, young or old. But for the Han people, he takes good care of them, and all who come to surrender are helped with great effort, gathering people to open up wasteland and cultivate fields. Moreover, he uses military law to restrain officials and historians, not allowing them to do evil. If you say Lü Bu only cares about military affairs and doesn't ask about government matters, then he can indeed gather scattered people, collect and settle the surrendered Qiang and Hu tribes, cultivate fields, build pastures, and handle affairs with speed and efficiency. In just one year, he was able to govern the northern regions in an orderly manner. If you say Lü Bu loves talent? Indeed. Lü Bu is generous to himself, has words that are accepted, and rewards are not meager. But he also threatened his own people, saying that if they didn't serve him, they would be killed. If you say Lü Bu is a good person, then he kills people like hemp. If you say he's a good official, then it seems he loves wealth and material goods.

  Jia Xu couldn't understand Lü Bu, so he was very cautious. When Lü Bu asked him, Jia Xu replied: "The Xiongnu king is wary of the rebellion by Zuo Xianwang and wants to eliminate him. The governor's prestige in the north is great, and the Xiongnu king will take this opportunity to ally with you, wanting to destroy the left wing and gain strength from both sides. However, our forces are too weak in the north and should not engage in a fierce battle with Zuo Xianwang. The Xiongnu king will first invite you, and then we will send troops to fight against Zuo Xianwang. Our army will choose the right moment to attack. In my opinion, our army should build up its military strength, divide into three routes, and cross the Yellow River. One route will be led by you, Governor, departing from Fuping and coordinating with the Xiongnu king's left and right wings, waiting for an opportunity to advance north and recover the counties of Beidi. The second route will be led by a brave general, departing from Shuofang and advancing westward to attack Linjing. This can assist our momentum, and also take advantage of the situation to cross the river and recover the counties of Shuofang and Linjing. The third route will be led by a capable general, secretly crossing the Yellow River and hiding in Jiluozhai. Our army and the Xiongnu king will attack Zuo Xianwang from both east and west, and he will have no way to escape southward, only able to flee north to surrender to the Xianbei. Although Jiluozhai is desolate, it is the only route for Zuo Xianwang's northern escape. Therefore, this place should be secretly guarded by a skilled general."

  Lü Bu listened intently, gazing at the sheepskin map. Jia Xu's words were perfectly reasonable, and the more he heard, the more they resonated with his own thoughts. He then praised Jia Xu, saying: "You are truly wise, with you by my side as an advisor, even if our troops are few, defeating the Xiongnu will be an easy matter."

  Lü Bu followed Jia Xu's words, bringing his personal guards and Hao Meng's troops, leading 2,500 cavalry out of Fuping, crossing the Yellow River to take over Lian County. Along the way, he appointed Zang Ba as a chief controller, leading the Beidi army to Shuofang, then joined forces with the Shuofang army, totaling 1,000 cavalry, crossed the river and directly attacked Linjing County. Another route was taken by Gao Shun as a chief controller, going to Shuofang to lead Yang Feng's wolf cavalry and the Beidi army, totaling 500 cavalry. They secretly crossed the Yellow River, hiding in Jiluozhai, waiting for Xianwang to be defeated. Only over a thousand cavalry remained, scattered among the ten counties of Beidi and Shuofang under the jurisdiction of Duan Jun, guarding county cities and various passes along the Great Wall. Due to the small number of defending soldiers, Lü Bu ordered before leaving that all counties in Beidi and Shuofang be on high alert, to prevent unexpected events from occurring.

  In mid-June, Lü Bu and the Southern Xiongnu Chanyu launched a pincer movement from east and west against Zuo Xianwang Che Niu and the Wusun tribes.

  The Chanyu first fought against the Wusun in the great tent of the Wusun. The Wusun asked for help from Che Nü, who gathered his troops and joined forces with the Wusun to fight a great battle against the Chanyu Qiangqu. Lü Bu took advantage of the situation to recover the west bank of the Yellow River, which originally belonged to Beidi County. Later, he followed Che Nü and attacked him and the Wusun, joining forces with the Chanyu to defeat Zuo Xianwang. Che Nü and the Wusun were unable to withstand the combined forces of Qiangqu and Lü Bu, so they fled north to Linjing, where they were ambushed by Zhang Bao's thousand cavalry. The two men lost half their troops and saw no way out, so they wanted to flee north and surrender to the Xianbei.