On October 13, 1600, the armies were still converging. Tokugawa Ieyasu (徳川家康) was marching west through Tōtōmi Province. Ishida Mitsunari (石田三成), lord of Sawayama Castle, held his position at Ogaki with the Western Army — 82,000 men on paper, the largest coalition the Sengoku era had assembled. He had built it through letters. Precisely worded, carefully timed, politically leveraged letters that had brought daimyo after daimyo into an alliance against Ieyasu's bid for dominance.

Mitsunari was not a battlefield general. He had never won a war. He was an administrator of almost supernatural ability — the man who had run Toyotomi Hideyoshi's bureaucracy, managed the logistics of the Korean campaigns, tracked every koku of rice and every sword counted in every domain. He had outmaneuvered rivals in politics, in court, in economic negotiation. He was perhaps the most powerful bureaucrat Japan had ever produced.

But on October 21, Sekigahara lasted three hours.

The collapse was rapid and total. Kobayakawa Hideaki (小早川秀秋), commanding 15,600 troops on Mount Matsuo, had already sent a secret letter to Ieyasu a week before the battle. When he charged down the mountain and struck Ōtani Yoshitsugu's (大谷吉継) forces from behind, four other wavering Western Army units defected simultaneously. The alliance Mitsunari had built through paperwork dissolved in an hour of blood and chaos.

Mitsunari fled east on foot. He did not go to his own Sawayama Castle — perhaps he knew it was already lost. He crossed Mount Aikawa in the autumn rain and disappeared into the Ibuki mountain region. He was helped by the head priest at Hokekyo Sanju-in Temple, who had been his childhood teacher. In some accounts, he hid in a pit beneath hay or refuse. He may have been there for two or three days.

The man who found him was Tanaka Yoshimasa (田中吉政). Not one of Ieyasu's great captains. A mid-tier daimyo who had signed a formal petition against Mitsunari before the campaign began, citing his arrogance and overreach. A man whose lands Mitsunari had once tried to confiscate through bureaucratic maneuvering during their days as Toyotomi allies.

Mitsunari was transported first to Ōtsu, then Ōsaka, then Kyoto. On November 5, 1600, he was paraded through the streets of Kyoto alongside Konishi Yukinaga (小西行長) and Ankokuji Ekei (安国寺恵瓊) — a deliberate public humiliation. The crowds jeered. Ieyasu wanted the populace to see the Western commanders brought low.

During the captivity, according to accounts, someone offered Mitsunari persimmons. He declined: they were bad for his stomach, he said. His captors laughed — what does a condemned man care about his stomach? He replied that as long as he lived, he would look after his health. The story became famous precisely because it captured something about him: even in defeat, utterly composed, refusing to behave as if the outcome had already been accepted.

On November 6, 1600, at Rokujōgawara (六条河原) — the traditional execution ground on the dry riverbed of the Kamo River in Kyoto — Mitsunari was beheaded alongside Konishi Yukinaga and Ankokuji Ekei. Their heads were displayed publicly.

He was 41 years old.

The administrative genius of the Toyotomi era had met a battlefield, and the battlefield had no use for administrative genius. The lesson would be absorbed by every daimyo who watched the heads displayed at the Kamo riverbed: in the new order, the sword outranked the seal.