Be beheaded by Sun Quan. In the twenty-fourth year of Jian 'an, Guan Yu launched the battle of Xiangfan. Although the Seventh Army was flooded and the important town of China was threatened, Jingzhou finally fell and was killed by Sun Quan himself. Zhu Ziyan, a professor of history at Shanghai University, wrote in the professional journal Collected Works of History that Guan Yu was defeated by the strangulation of the Wu-Wei alliance, but Zhuge Liang, a member of his own family, may have really sent Guan Yu to the guillotine.

Extended data:

In the twenty-fourth year of Jian 'an (2 19), Guan Yu sent troops to take Fancheng, then flooded the three armies and escaped from the Pound ban, which was famous all over the world. Cao Cao was frightened and even prepared to move the capital. But Sima Yi saw clearly that Guan Yu could not go far if the Wei Shuwu family didn't want him to go too far.

Sun Quan acted, and Lv Meng entered Jingzhou in white and occupied Jingzhou. Imagine that if Zhuge Liang had sent Zhao Yun to guard Jingzhou before, ten Lv Meng would have come for nothing.

Guan Yu, a spent force ahead, was finally defeated by Huang Xu and retreated to Maicheng. At this time, Liao Hua went to Shang Yong for help. Who is the commander of Shang Yong? Liu Feng, adopted son of Liu Bei. It is puzzling that Liu Feng refused to save Guan Yu. Would Liu Bei or Zhuge Liang not dare to save Guan Yu if he didn't express or hint?

In this way, with Cao Cao in front and Sun Quan behind, Liu Bei can't be saved, and Guan Yu can't be defeated even if he has three heads and six arms. Finally, Guan Yu was captured by the State of Wu.

References:

Guan Yu-Baidu Encyclopedia