Wu Guang was born in Yangxia (陽夏; present-day Taikang County, Zhoukou, Henan), and his courtesy name was Shu.
[2] In August or September 209 BC,[3] he was a military captain along with Chen Sheng when the two of them were ordered to lead 900 soldiers to Yuyang (漁陽; southwest of present-day Miyun County, Beijing) to help defend the northern border against Xiongnu.
They announced that Fusu, the crown prince of Qin, who had wrongly been forced to commit suicide, and Xiang Yan (項燕), a general of Chu, had not died and were joining their cause.
Using 900 men to resist an empire seemed to be a suicidal move, but the people, who had felt deeply oppressed by the Qin regime, joined Chen Sheng and Wu Guang's cause quickly.
They wanted to change Wu Guang's plans, end the siege of Xingyang, and face Zhang Han's forces directly.