Anti-European attitudes began under Hideyoshi, whose suspicion of the Europeans first began with their intimidating appearance; their armed ships and sophisticated military power produced doubt and distrust, and following the conquest of the Philippines by the Spanish, Hideyoshi was convinced they were not to be trusted. The true motives of the Europeans came quickly into question.

The Sakoku Edict of 1635 was a Japanese decree intended to eliminate foreign influence, enforced by strict government rules and regulations to impose these ideas. It was the third of a series issued by Tokugawa Iemitsu, shōgun of Japan from 1623 to 1651. The Edict of 1635 is considered a prime example of the Japanese desire for seclusion. The Edict of 1635 was written to the two commissioners of Nagasaki, a port city located in southwestern Japan. Only Nagasaki Island is open, and only to traders from the Netherlands.

The key points of the Edict of 1635 included:

• The Japanese were to be kept within Japan’s own boundaries. Strict rules were set to prevent them from leaving the country. Anyone caught trying to leave the country, or anyone who managed to leave and then returned from abroad, was to be executed. Europeans who entered Japan illegally would face the death penalty too.
• Catholicism was strictly forbidden. Those found practicing the Christian faith were subject to investigation, and anyone associated with Catholicism would be punished. To encourage the search for those who still followed Christianity, rewards were given to those who were willing to turn them in. Prevention of missionary activity was also stressed by the edict; no missionary was allowed to enter, and if apprehended by the government, he would face imprisonment.
• Trade restrictions and strict limitations on goods were set to limit the ports open to trade, and the merchants who would be allowed to engage in trade. Relations with the Portuguese were cut off entirely; Chinese merchants and those of the Dutch East India Company were restricted to enclaves in Nagasaki. Trade was also conducted with China through the semi-independent vassal kingdom of the Ryukyus, with Korea via the Tsushima Domain, and also with the Ainu people through the Matsumae Domain.