"Baihu" was not Yan's real name, but a nickname given to him due to his physical prowess or skin color; thus his name should be translated to "White Tiger Yan". According to Chen Shou's Records of Three Kingdoms, Yan held gigantic influence among the Shanyue tribes and even Han officials in the Wu area. When Liu Yao was appointed as Governor of Yang Province, Yan was approached and bribed by Liu to support him against the warlord Yuan Shu, who had a large army in the Huai River valley.
After Liu Yao was defeated by Yuan Shu's ally and subordinate, Sun Ce, Yan successfully re-established or even increased his private army to tens of thousand, composed of elite Shanyue people and bandits, to prepare a final showdown with Sun Ce. Besides being the head of a loose confederation of bandits and local officials, Yan formed an alliance with a warlord, Wang Lang, who had plenty of food supplies that can afford the alliance's soldiers.
Despite Yan's preparations, Sun Ce was able to outwit Wang Lang and took his supply base through tactic; with provisions gone, Yan and Wang Lang were defeated by Sun. Yan then fled into the hills, and continued to encourage the Shanyue people to oppose Sun Ce's reign.
In the historical novel Romance of the Three Kingdoms, Yan was attacked by Sun Ce and then fled to Wang Lang to seek help. While seeking the help of Wang Lang, however, his army was defeated by Ling Cao and his son, Ling Tong. During Yan's retreat, Dong Xi caught up with him, however, and slew him. Dong Xi then sent Yan's head in a box to Sun Ce.
Historically, it was likely that Yan was defeated by Sun Ce's vanguard Ling Cao, however, he did survive the rout, and at least lived up to the time of Sun Ce's assassination.
- de Crespigny, Rafe (2004) Generals of the South: the foundation and early history of the Three Kingdoms state of Wu. Canberra: Australian National University. Internet Edition.