Every boot that hit the 東海道 (Tōkaidō) that morning meant something. Tokugawa Ieyasu, fifty-seven years old and closer to absolute power than any man since Toyotomi Hideyoshi, was moving west at the head of roughly thirty thousand soldiers. Behind him: Edo, the city he had built from marshland into a military capital. Ahead: a reckoning at a mountain pass called Sekigahara that would either end a century of civil war or undo everything he had spent his life constructing.

The political groundwork was already in place. The Western Army's critical fortress, Gifu Castle, had fallen to Ieyasu's eastern allies on September 29 — more than a week before. The momentum had shifted. Eastern Army generals like Fukushima Masanori had been fighting without Ieyasu; he was racing westward not to start the campaign but to be present for its conclusion. In a real sense, the phrase 天下分け目 (tenka wakeme) — "the division of the realm" — was already being applied to what was coming. Everyone knew.

The march itself was a statement. The 東海道 (Tōkaidō) — the "Eastern Sea Road" — connected Edo to Kyoto along the Pacific coast, passing through fifty-three post-stations across roughly five hundred kilometers. It was Japan's greatest highway, the artery along which commerce, armies, and power flowed. When Ieyasu committed his personal army to that road, there was no ambiguity about the destination or the stakes.

The plan had an elegant symmetry. Ieyasu would take the coastal Tōkaidō — the faster route, lower passes, better supply roads. His son Hidetada would take the parallel 中山道 (Nakasendō), the mountain road cutting through the interior of Honshū, commanding thirty-eight thousand men. This was, remarkably, a larger force than his father's. The most powerful single Tokugawa column was the one entrusted to a twenty-one-year-old commanding an army for the first time.

The strategy was convergence: both forces would meet west of the mountains in time for the decisive engagement. Simple enough in principle.

What Ieyasu could not yet know on October 7 — because it had not yet happened — was that the plan was already beginning to fail.

Hidetada had reached Karuizawa on the Nakasendō that same day, placing him roughly two days' march from Ueda Castle. Ueda was held by Sanada Masayuki, a brilliant and veteran commander who had fought on the Western side. More to the point, Masayuki had defeated a Tokugawa army at Ueda Castle in 1585 — humiliating the clan, killing hundreds of their soldiers with a fraction of their numbers. That defeat lived in Tokugawa memory with the particular rawness of a wound that had never been settled.

For a young man raised in that family, two days' march from an old score felt very close.

Ieyasu, meanwhile, moved with the efficient certainty of a man who had been building toward this campaign for years. He covered the leg from Edo to Suruga Province in roughly five days, passed through the towns of Shinano and Mikawa, and arrived at Akasaka on October 20 — the night before the battle. His generals were waiting. The Western Army was positioned at Sekigahara.

The next morning, Ieyasu won. The battle lasted perhaps six hours. The Kobayakawa clan's defection at a critical moment shattered the Western lines, and by late morning it was over. Japan had a new master.

Hidetada and his thirty-eight thousand men were not there. They were still fighting their way out of a detour that had consumed eight precious days and accomplished nothing. When Hidetada finally arrived at Sekigahara on the evening of October 21, the battle was done and the dead had been counted. His father, by all accounts, did not speak to him warmly.