When 徳川家光 (Tokugawa Iemitsu), the third Tokugawa shogun, issued the edicts that completed 鎖国 (sakoku — 'the locked country'), he was doing something no major civilization had ever attempted so deliberately: voluntarily sealing an entire nation from the outside world and daring the world to knock. He was thirty-two years old. His father, 徳川秀忠 (Tokugawa Hidetada), the second shogun, had begun the crackdowns; Iemitsu would finish them.

The policy did not arrive in a single proclamation. It came in five waves between 1633 and 1639, each one tightening the seal. The 1633 edict restricted travel and trade. The 1635 edict — the most sweeping — forbade every Japanese subject from leaving Japan on pain of death; those who had already left could never return. The 1636 edict expelled 287 Portuguese non-traders, including Japanese wives and mixed-race children, relocating them to Macau while confining the remaining Portuguese merchants to 出島 (Dejima), a small fan-shaped artificial island in Nagasaki harbor. The final edict, in 1639, expelled the Portuguese entirely.

The driving fear was not primarily economic. It was political. Christianity had shown the Tokugawa what an ideology that answered to a foreign authority — the Pope in Rome — could do to a society. The Shimabara Rebellion of 1637–38, in which roughly 40,000 mostly Christian peasants rose up against the shogunate, proved the point in blood. The rebels were crushed. The Portuguese, suspected of having encouraged them, were expelled the following year.

The Dutch were spared. Unlike the Portuguese and Spanish, the Dutch East India Company had never sent missionaries. They came for trade and nothing else. For this, they were rewarded with a monopoly — confined to Dejima, forbidden to leave without permission, required to perform an annual ritual demonstrating they were not Christians. Their annual trade mission to Edo became one of the strangest spectacles of the era: foreign merchants parading through the Japanese capital like supplicants at court.

The ban applied to Japanese subjects as strictly as to foreigners. A Japanese sailor shipwrecked on a foreign shore who somehow found his way home faced execution for having left. The country did not merely close its gates — it built a wall around the very impulse to see what lay beyond them.

The irony noted by later historians is that the Japanese did not even have a word for what they were doing while they were doing it. The term 鎖国 (sakoku) — literally 'chained country' — was coined in the late Edo period by a scholar translating a Dutch text. For most of the period, the Japanese simply called the edicts 'the laws of the realm,' as if it were self-evident that realms should be sealed.

For the samurai, sakoku meant something unexpected: peace. With Japan's ports closed, there were no foreign wars to fight, no new territories to conquer. The warrior class that had battled for a century slowly transformed into bureaucrats and scholars. They wrote treatises on the code of Bushido (武士道, Bushidō) to give meaning to a peacetime that made their martial skills largely ceremonial. Sakoku was simultaneously the shogunate's greatest achievement and the beginning of its long internal decay.

When Commodore Perry arrived in 1853 with steam-powered warships and demanded that Japan open its ports, Japan discovered in a single afternoon exactly how far the world had moved on. The two centuries of self-imposed stillness had preserved the Tokugawa order — and left Japan militarily and technologically outpaced by nations it had stopped watching. The shock of Perry's arrival set in motion the chain of events that ended the samurai era within fifteen years.