Cao Hongda was born in 882, during the reign of Emperor Xizong of Tang. His father Cao Gui was a general under Qian Liu, who would eventually control the region that became the territory of Wuyue. Cao Hongda was born at Linping. After he grew older, Cao Gui wanted to train him physically, so Cao Gui had him eat with servants and not be given warm clothing even when it was in the winter. Cao Gui also had him lift bricks daily. After Cao Hongda grew yet older, he became a guard at the headquarters for one of the circuits Qian controlled, Zhendong Circuit. At that time, his father Cao Gui served as the prefect of Su Prefecture, and wanted to enter into a marital alliance with a fellow general under Qian, Chen Xun the prefect of Mu Prefecture — by having Cao Hongda marry one of Chen's daughters. He thus sent Cao Hongda on a mission to Mu, intending to have him marry Chen's daughter there. However, a fortuneteller informed Cao Hongda and/or Cao Gui, "The Chens are not appropriate for your marital relationship. You should marry with another family to bring glory and honor on you." When he went through the Qiantang, the capital of Qian's main circuit, Zhenhai Circuit, Qian was impressed by Cao Hongda's appearance, and therefore gave him a younger sister in marriage. Cao Hongda thereafter successively served as the prefect of Tai Prefecture, then of Chu Prefecture.
Service under Qian Yuanguan
Qian Liu, who then carried the title of King of Wuyue, died in 932, and was succeeded by his son Qian Yuanguan. Qian Yuanguan, who did not take the title of king but only that of military governor of Zhenhai and Zhendong initially, put Cao Hongda in charge of the affairs of the state — effectively, to be chancellor, although not with that title as Qian Yuanguan was not claiming, at that point, statehood. When Qian Yuanguan claimed the title of king in 937, he commissioned Cao, along with Shen Song and Pi Guangye, chancellors. He was said to be kind and honest, often donating food to the needy. Qian Yuanguan honored him greatly and referred to him only as "the Chancellor" rather than by name.
Service under Qian Hongzuo
Qian Yuanguan died in 941 and was succeeded as king by his son Qian Hongzuo — as Qian Hongzun had died earlier. During Qian Hongzuo's mourning period, Cao Zhongda served as regent. When there was subsequently a disturbance among the army ranks where the soldiers claimed that there was unfairness in the rewards given to them, Cao personally met the soldiers to comfort them. He died in 943.
