The () or sea ban was a series of related isolationist policies restricting private maritime trading and coastal settlement during most of the Ming Empire and early Qing Empire. Despite official proclamations the Ming policy was not enforced in practice, and trade continued without hindrance. The early Qing dynasty's anti-insurgent "Great Clearance" was more definitive with devastating effects on communities along the coast. First imposed to deal with Japanese piracy amid the mopping up of Yuan partisans, the sea ban was completely counterproductive: by the 16th century, piracy and smuggling were endemic and mostly consisted of Chinese who had been dispossessed by the policy. China's foreign trade was limited to irregular and expensive tribute missions, and the military pressure from the Mongols after the disastrous Battle of Tumu led to the scrapping of Zheng He's fleets and scrapping of shipbuilding. Piracy dropped to negligible levels only upon the end of the policy in 1567, but a modified form was subsequent
A pesar de las proclamaciones oficiales, la política Ming no se aplicó en la práctica, y el comercio continuó sin obstáculos. La antigua política antiinsurgente de la dinastía Qing "Great Clearance" era más definitiva con efectos devastadores en las comunidades a lo largo de la costa. El comercio exterior de China se limitó a las misiones de tributo irregulares y costosas, y la presión militar de los mongoles después de la catastrófica Batalla de Tumu llevó a la destrucción de las flotas de Zheng He y la destrucción de los buques.