Iyemitsu Tokugawa (Photo courtesy of Wikipedia)
In 1635, the third Tokugawa shogun, Iyemitsu (Iemitsu) Tokugawa (reigned: 1623-1651), issued the Sakoku Edict of 1635. The edict enforced the restriction of Japanese migration out of the Japanese Empire and the closure of Japan's ports from international trade. Nagasaki was left open though, but only for limited Chinese and Dutch traders.

The edict had its purpose anyway, and perhaps may have served well the initial aims of the shogunate. The Japanese shogun wanted an increase of domestic output, and when it worked, population grew. Edo (later, Tokyo) grew to a population of one million by the year 1700. However, the act of seclusion from the world made Japan lag behind the fast verging change taking over the world in the next two centuries.

Now, of course there must be a reason, or reasons, behind this act of seclusion by the Tokugawa shogunate.

The most imposing reason is the spread of Catholicism in Japan. It began when St. Francis Xavier (a church with his name is in my locality) went to Japan as a Portuguese missionary in 1549. During the long campaigns of Oda Nobunaga from the 1560s until his death in 1582, the dictator daimyo promoted the spread of Catholicism in Japan. This was to counter the influence of Buddhism in Japan, which had monks at Mount Hiei ready to take Kyoto if had he not occupied the city first. At its peak, there were around 300,000 Japanese Catholics in the country.

Fort Santiago (Photo courtesy of Wikipedia)
Second to the Portuguese in the number of missionaries in Japan were the Spanish, which had a colony near Japan, the Philippines. The Spanish had established New Castille in a city in Southern Luzon called Manila by 1571, and built an imposing walled city, Intramuros, by 1590, which King Philip II himself saw as a costly endeavor.

Well, Nobunaga's successor, Toyotomi Hideyoshi, began to eye the Philippines not only because it was geographically near Japan, but also because of the number of missionaries it had been sending to Japan. Most Spanish missionaries have to go to Manila first before Japan, and Hideyoshi did not like Catholicism, at least, in the latter period of his reign in the 1590s. Hideyoshi did not continue to send an invasion to the Philippines though, mainly because a peace envoy, a Spanish missionary, had talked the Japanese leader out of it. Still, persecution continued in Japan, which even resulted to around 27,000 dead at Shimabara, 1637.

One not-so-obvious reason to us today is the influence of Spanish Manila in Asian trade. It had replaced Japan as the entrepot of Western trade in the Asia-Pacific region because of the galleon trade. Also, Manila begun to attract many Chinese, which was a signal that the city was a flourishing one. Even if Manila had no large navy like Hideyoshi used to invade Korea, its economic clout, feared the Tokugawa shogunate, might take over Japan's ports. Therefore, Japan closed her doors from the world in fear of Manila's influence.

As the saying goes, it is more than meets the eye.

See the references here.