Cao Cao was born in the county of Qiao in 155. His father Cao Song was a foster son of Cao Teng, who in turn was one of the favorite eunuchs of Emperor Huan. Cao Cao was known for his craftiness as a young man. According to the Biography of Cao Man, Cao Cao's uncle often complained to Cao Song regarding Cao Cao's childhood indulgence in hunting and music with Yuan Shao. To counter this, Cao Cao one day feigned a fit before his uncle, who hurriedly informed Cao Song. Cao Song rushed out to see his son, who then acted normally. When asked, Cao Cao replied, "I have never had such illness, but I lost the love of my uncle, and therefore he had deceived you." Henceforth, Cao Song ceased to believe the words of his brother regarding Cao Cao, and thus Cao Cao became even more blatant in his wayward pursuits.
At that time, there was a man living in Runan named Xu Shao who was famed for his ability to evaluate one's potentials and talents. Cao Cao paid him a visit in hopes of receiving the evaluation that will earn him some reputation politically. Originally Xu Shao pondered and refused to make a statement; however, under persistent questioning, he finally said, "You would be a capable minister in peaceful times and an unscrupulous hero in chaotic times." Cao Cao took this as a compliment and was very pleased as it was recorded that he "laughs and leaves" after receiving said comment. It is worth noting that there are two other versions of the comment in other unofficial historical records: "capable minister in peaceful times, righteous hero in chaotic times" and "sinister foe in peaceful times, great hero in chaotic times."
Alliance against Dong Zhuo
In 189, Emperor Ling died and was succeeded by his eldest son, though it was the empress dowager and the eunuchs who held true power. The two most powerful generals of that time, He Jin and Yuan Shao, plotted to eliminate the clan of influential eunuchs. He Jin summoned Dong Zhuo, governor of Liang province (凉州), to lead his army into the capital Luoyang to lay pressure on the empress dowager, despite numerous objections on account of Dong Zhuo's reputation and personality.
Before Dong Zhuo arrived, however, He Jin was assassinated by the eunuchs and Luoyang fell into chaos as the supporters of Yuan Shao battled the army of eunuchs. Dong Zhuo's elite army, assigned to him due to the importance of his position as safeguard of the border, easily rid the palace grounds of opposition. After he deposed the previous emperor, Dong Zhuo placed on the throne the puppet Emperor Xian. While Dong Zhuo did desire personal power with this opportunity, he did want to restore the Han Dynasty and resolve the political conflicts. From a previous encounter, he deemed that Emperor Xian was more capable than the original puppet Emperor.
After rejecting Dong Zhuo's appointment, Cao Cao left Luoyang for Chenliu (陳留), southeast of present day Kaifeng, Henan, Cao Cao's home town), where he raised his own troops. The next year, regional warlords combined their forces under Yuan Shao against Dong Zhuo. Cao Cao joined their cause. China fell into civil war when Dong Zhuo's own foster son, Lü Bu, eventually killed him in 192.
Securing the emperor
Through short-term and regional-scale wars, Cao Cao continued to expand his power.
In 196, Cao Cao found Emperor Xian and convinced him to move the capital to Xuchang as per the suggestion from Xun Yu and other advisors (as Luoyang was ruined by war and Chang'an was not under Cao Cao's military control), and he was proclaimed Chancellor. Cao Cao was then instated as the General-in-Chief (大將軍) and Marquis of Wuping (武平侯), though both titles had little practical implication. While some viewed the Emperor as a puppet ruler under Cao Cao's power, Cao Cao himself adhered to a strict personal rule to his death that he would not usurp the throne. Later in his life, when he was approached by his advisors to take over the Han Dynasty and start a new rule, he replied, "If heaven bestows such fate on me, let me be the King Wen of Zhou."