明实录
A 1472 entry in the Ming Shilu reported that when some Chinese from Nanhai county escaped back to China after their ship had been blown off course into Vietnam, where they had been forced to serve as soldiers in Vietnam's military. The escapees also reported that they found out up to 100 Chinese men remained captives in Vietnam after they were caught and castrated by the Vietnamese after their ships were blown off course into Vietnam. The Chinese Ministry of Revenue responded by ordering Chinese civilians and soldiers to stop going abroad to foreign countries. China's relations with Vietnam during this period were marked by the punishment of prisoners by castration.