Cao Cao again launches a campaign to conquer Hanzhong in 215.

Initially, Zhang Lu has no hope of standing against Cao Cao's armies, and plans to surrender.

His younger brother Zhang Wei, however, insists on fighting and leads his army against the invading forces.

He is soon killed in battle, and again Zhang Lu considers surrendering.

His advisor Yan Pu tells him that in surrendering so readily, they would have no position to negotiate from.

Instead, Zhang Lu retreats to his fortress at Bazhong.

When leaving his capital, he does not destroy his wealth and treasures, nor attempt to take them with him, instead leaving them behind saying "These things belong to the country, not to me."

Cao Cao is greatly impressed by this, and sends a messenger to Zhang Lu asking him to surrender.

Yan Pu's plan is successful, as Zhang Lu and his forces are warmly welcomed by Cao Cao.

He is given the title General who Suppresses the South and his five sons are granted the rank of marquis.

He marries his daughter to a younger son of Cao Cao, Cao Yu.

As further demonstration of the bad blood between Zhang Lu and Ma Chao, when Cao Cao turns Ma Chao's son Ma Qiu over to Zhang Lu, he immediately executes him.

Following Cao Cao’s defeat of Zhang Lu and subsequent seizure of Hanzhong, Sima Yi and Liu Ye advise him to take advantage of the victory to attack Yi Province, since it is still unstable under Liu Bei's new government and Liu himself is away in Jing Province.

Cao Cao refuses and leaves Xiahou Yuan, Zhang He and Xu Huang to defend Hanzhong.