In 190 the eastern governors rose against Dong Zhuo in name. There was contact near Sishui and Hulao, but each lord kept his own ground and few pursued. Cao Cao marched west with his own men, was beaten by Xu Rong at Xingyang, and took an arrow.
The novel gathers this loose war into the three heroes fighting Lü Bu under Hulao. Liu Bei, Guan Yu, and Zhang Fei did not yet have their later rank. Lü Bu really was in Dong Zhuo’s army. Their joint victory over him is not reliably recorded. The year and the failed alliance are real. The famous scene is the novel.