Lu Xun was married to Sun Ce's daughter. He was appointed in Lukou to replace Lu Meng as part of his plans to catch Guan Yu off his guard. To make Guan Yu became so conceited that he will withdraw his troops from Jingzhou to send them against Fankou to the north, he sent a humble letter of friendship with gifts of food and wine. Guan Yu disregarded the gesture as a weak plea. Later, when half of the troops of Jingzhou assailed to the north, Lu Xun helped Lu Meng win the territory back from Shu.
     When Emperor Liu Bei of Shu came eastward seeking revenge for Guan Yu's death, Sun Quan promoted Lu Xun to the defense of Wu as Commander-in-Chief. Yet the Shu army surged towards them in great numbers, positioning men in camps stringing from Yiling, in the west, through Jingzhou.
     The generals in Lu Xun's command were veterans of war and many had noble backgrounds. they were anxious to show off their prowess and overrun the Shu army. However, Lu Xun held them back by saying, "Liu Bei is leading his entire army and their fighting spirit is at its peak. Examine their positions closely, they camp on steer and rugged land. We cannot attack them from below. Yet, they have many disadvantages : they are avoiding the plains area and there is a possibility of an incursion from the north. Therefore Liu Bei is in a quandary from where he sits. Though I know that rocky land would inhibit anyone in war, the same land will wear down their spirits if we stall. We must wait, bring them slowly and gently under our control." His reasoning convinced his generals they would succeed.
     After a long standstill, the Shu army was worn with fatigue, and seemed too weary to break the deadlock. At that point Lu Xun began his offensive. He used incendiary attacks and utterly crushed the defense. Though his generals wanted to chase after Liu Bei, who had retreated to the Palace of Eternal Peace, once again Lu Xun restrained them. He feared an attack by Cao Pi, who had troops stationed near the border. He calmly drove away the three armies of Wei.
     Sun Quan relied on Lu Xun to restore ties between Shu and Wu, he was even allowed to revise letters delivered to Shu. Entrusted with such great decisions, it seemed as if Lu Xun himself held the imperial seal of the Wu kingdom in his own hand.