As a teenaged student Cao was an enthusiastic supporter of the Northern Expedition and attempted to join the National Revolutionary Army, although he was rejected on account of his age.

He and a friend got a letter of recommendation from the local party secretary and walked the 120 miles to find the Chinese Red Army.

He got an opportunity to serve as a division commander during the fourth anti-encirclement campaign when his superior officer was wounded, and proved capable in battle.

In the leadership struggles that took place during the Long March, Zhang Guotao had Cao purged from the Party and dismissed from his army post.

[2] After a brief stint with the Eighth Route Army at the start of the Second Sino-Japanese War, Cao would spend the next 5 years as chief of staff of the Left-behind Corps.

[2] In the aftermath of Japan's surrender, Cao Lihuai led the regiment of soldiers that escorted Lin Biao and Xiao Jinguang from Puyang to Manchuria.

On December 14, 1945, he was forced to withdraw from the urban area of Changchun because of discipline problems with the local militias that had been recruited into the new People's Liberation Army.