In the 12th year of the reign of Duke Ding of Lu, Confucius became the prime minister of Lu state. In order to enhance the status of the loyal family of Duke Ding, Confucius put forward the plan of undermining the power of three counties. Those three counties are Hou County, Fei County and Cheng County of Lu state, which are the private territories of Shu family, Ji family and Meng family respectively. Confucius said, "Officials can't hide weapons privately, and Da fu can't own a city with a circumference of more than 300 zhang (a unit of length, 1 zhang = 10.94 foot). Now those three families have violated the regulations, please give orders to undermine their power." Confucius then sent his disciples Zigao and Zilu to implement this plan. Gongshan Buniu, a retainer of the Ji family in Fei County, launched a rebellion and attacked the capital Qufu. Confucius himself led his disciples to defeat the rebels of Gongshan. Later, the fortifications of Fei County and Hou County were dismantled. However, Gonglian Chufu, a retainer of Meng family in Cheng County, opposed the dismantlement of the county's fortifications, and the Meng family also secretly supported him. As a result, Duke Ding personally went on a punitive expedition but failed. Besides, the army of Qi state was sent out to the border to support the Meng family, forcing the army of Lu state to retreat.