Wang Kai (Han dynasty)

Wang Kai was an advisor to the warlord Lü Bu during the late Han Dynasty.

Biography
Wang Kai originally served as an official under the warlord Cao Cao. In 194 when Cao Cao was attacking Xu Province, Wang Kai, along with Zhang Miao, Chen Gong, Zhang Chao (張超, Zhang Miao's younger brother) and Xu Si (許汜), betrayed Cao Cao and defected to Lü Bu, giving up Cao's base in Yan Province to Lü Bu.

When Lü Bu was besieged by Cao Cao's forces at the Battle of Xiapi in 198, Wang Kai and Xu Si advised Lü Bu to seek reinforcements from Yuan Shu. Lü Bu agreed to their suggestion. Yuan Shu initially declined to help Lü Bu, but when Wang Kai and Xu Si warned him that if Lü Bu was defeated, Yuan Shu would face the same fate. Yuan Shu then prepared his troops for battle but did not actually send them to reinforce Lü Bu. There were no records about Wang Kai in history after his meeting with Yuan Shu.

In fiction
Wang Kai and Xu Si appear in Luo Guanzhong's historical novel Romance of the Three Kingdoms as Lü Bu's advisors. Similarly, during the Battle of Xiapi, both of them urged Lü Bu to seek help from Yuan Shu. Lü Bu agreed and sent Zhang Liao and Hao Meng to cover the two advisors as they broke out of the siege. Wang Kai and Xu Si later returned and informed Lü Bu that Yuan Shu said he wanted Lü Bu to send his daughter over to marry his son first before he would send reinforcements.