Why did Shi Huangdi tear down the walls of Chinese Kingdoms?

Shi Huangdi tore down the walls of various Chinese kingdoms as part of his strategy to consolidate power and establish a centralized empire. By tearing down the walls, he aimed to eliminate potential threats from rival states and prevent their resurgence. This action allowed him to annex these kingdoms and unify them under his rule. Additionally, the removal of these walls prevented internal trade barriers and promoted economic growth and cultural exchange within his empire.