Repercussions

The destruction of the Toyotomi at Osaka in 1615 opened the Pax Tokugawa — a period of internal peace in Japan lasting until the shogunate's collapse in 1868, unmatched in duration by almost any comparable state in the early modern world. It was purchased entirely by force: every daimyō capable of contesting central authority had been eliminated, absorbed, or reduced to manageable size by the time Hideyori died, and the Tokugawa spent the next two and a half centuries administering the result rather than fighting for it.

Hideyori and his mother Yodo-dono took their own lives as Osaka Castle burned in June 1615; Hideyori's young son, the last direct heir, was found afterward and executed. It closed the unification cycle exactly where it began — with an entire clan destroyed and its heirs killed, the same method Nobunaga had used on the Azai and Hideyoshi on the Shibata, now turned by Ieyasu on Hideyoshi's own bloodline. A war fought in the name of completing Hideyoshi's project ended by erasing the family that had led it.

Sekigahara is routinely called the battle that decided the realm, and it is worth being precise about what it actually decided. Ishida Mitsunari's cause was the more legitimate one on the historical record — defending Hideyoshi's five-year-old heir against a regent's naked ambition. A single mid-battle defection replaced that legitimacy with Ieyasu's raw military power in an afternoon, and everything that followed, including the eventual destruction of Hideyoshi's own son fifteen years later, flowed from that afternoon rather than from any prior claim of right.

Ieyasu took the title of shōgun in 1603, formalising what Sekigahara had already decided in practice, and retired the title to his son within two years while retaining the actual power — establishing the pattern of hereditary rule behind a formally retired shōgun that the Tokugawa house would maintain, with adjustments, for fifteen generations. The office had existed since the twelfth century, but the Tokugawa turned it into something closer to a genuine centralised state than any of its predecessors had managed.

The Tokugawa formalised sankin-kōtai — a system requiring every daimyō to maintain a residence in Edo, spend alternating years there under the shogunate's direct observation, and leave family as hostages when they returned to their own domains. It was, in effect, Odawara's principle of overwhelming scale turned into permanent bureaucratic practice: no domain could accumulate the resources to challenge Edo, because a large fraction of every domain's wealth was spent constantly moving its lord and retinue back and forth along roads the shogunate controlled.

Hideyoshi's 1590 reassignment of Ieyasu to the marshy, unpromising territory around a fishing village called Edo was intended as a demotion. Ieyasu turned it into the future Tokyo, and sankin-kōtai's requirement that every daimyō maintain a household there — plus the merchants, artisans, and service economy that grew up to support tens of thousands of samurai retinues cycling through the city — made Edo, by the eighteenth century, the largest city in the world by population, larger than London or Paris.

The Tokugawa, having just spent fifty-five years watching one clan after another destroy the next in a contest partly fuelled by foreign contact — Christian daimyō, European firearms, Date Masamune's independent diplomacy with Rome — closed the country almost entirely. Foreign trade was restricted to a single artificial island at Nagasaki housing Dutch merchants; Japanese subjects were forbidden to travel abroad on pain of death; Christianity, associated with European political influence, was violently suppressed. The policy held for over two centuries, until American warships forced its end in 1853.

In 1613, while the shogunate was still consolidating power, the northern lord Date Masamune sent his own ambassador, Hasekura Tsunenaga, on an independent diplomatic mission to Rome and the courts of Europe, seeking direct trade relationships years before Edo's isolationist instincts hardened into policy. The mission reached Madrid and Rome and returned in 1620 to a Japan that had already begun persecuting Christians and closing itself off; its results were quietly abandoned, and it stands as the clearest evidence of how briefly an alternative, more open trajectory for Japan remained possible.

The Tokugawa peace and the sakoku isolation it maintained left Japan without modern weapons, industry, or diplomatic experience when American warships under Commodore Perry forced the country open in 1853. The shock discredited the shogunate so completely that it collapsed within fifteen years, replaced by the Meiji Restoration's crash industrialisation and militarisation under a restored emperor — a reaction against two and a half centuries of the very stability the unification wars had been fought to produce.

Nagashino in 1575 is usually cited as the battle that ended the supremacy of the mounted samurai charge in Japanese warfare — roughly 3,000 Oda arquebusiers in rotating firing ranks, using a river and marshy ground to funnel the Takeda cavalry into continuous fire, destroyed the finest cavalry force in Japan in an afternoon. Japan and Europe arrived at the identical tactical conclusion in almost exactly the same decade — the Netherlands would relearn the same lesson against Spanish tercios at Nieuwpoort a generation later — entirely independently of each other.

Hideyoshi, a peasant's son who had risen to rule Japan, spent his last years making sure nobody after him could do the same thing. His 1588 sword hunt confiscated weapons from the peasantry under the pretext of funding a great Buddha statue, disarming the class from which he himself had come; subsequent edicts fixed occupational and social status by birth, formally separating samurai from farmers from merchants in a way earlier Sengoku Japan's fluid, ability-based social mobility had never enforced. The century of civil war that had let a sandal-bearer become absolute ruler ended by making that impossible ever again.

The burning of the Enryaku-ji on Mount Hiei in 1571 and the eventual surrender of the Ikkō-ikki confederation at Ishiyama Hongan-ji in 1580, after a full decade of siege, together ended the presumption that had governed Japanese politics for centuries: that religious institutions, however armed or however popular, existed outside the reach of secular military power. Osaka Castle was later built directly on the ruins of the Ikkō-ikki's temple — the site of a peasant faith's last stand becoming the seat of the very centralising power that had destroyed it, and later the site of the Toyotomi's own destruction in turn.