What happened
Under the third shogun, Iemitsu, a series of edicts (1633–1639) banned Christianity, barred Japanese from traveling abroad or returning, and expelled the Portuguese (1639, after the Shimabara Rebellion of 1637–38).
Foreign contact was narrowed to managed channels: the Dutch on the islet of Dejima and Chinese merchants at Nagasaki, Korea via Tsushima, Ryukyu via Satsuma, and the Ainu trade via Matsumae.
Background
Modern historians stress that this was selective engagement rather than total isolation — the word sakoku itself was coined only in 1801. Western science still seeped in as “Dutch learning” (rangaku).
Consequences
Two centuries of internal stability and a distinctive urban culture followed. The order ended with Perry’s arrival in 1853 and the Treaty of Kanagawa in 1854 — leaving Japan a rushed 19th-century catch-up once the doors opened.