Since the Ming dynasty ( founded in 1368 ), a series of sea bans ("haijin") restricted China's foreign commerce, at times attempting to ban it completely. In 1684, the Kangxi Emperor of the Qing Dynasty allowed foreigners to trade with China in the four cities of Guangzhou, Xiamen, Songjiang, and Ningpo. In the case of Guangzhou, early traders were obliged to follow the monsoon winds, arriving between June and September, conducting their business, and then departing between November and February. The foreign ships were anchored downstream at Pazhou (then known as "Whampoa"), with business conducted in the city's western suburbs. Western traders were further required to work through Chinese merchants who would guarantee their good behavior and tax obligations; they were also the owners and landlords of the warehouses and apartments the traders were obliged to use. In practice, private traders could often avoid these restrictions but the customs superintendent, the "hoppo", was always careful to enforce them upon large-volume purchasers such as the East India Company. Typically, cargo was ferried from the ships by its own crew and to the ships at the expense of the Chinese merchants on their "chop boats" (lighters). To avoid theft or piracy, foreign traders began assigning a few of their own seamen to these ships as guards.