Tanba: The Ten-Year Pacification That Forged Nobunaga's Most Dangerous General

Akechi Mitsuhide was made in Tanba. Seven years before the Honnō-ji Incident, when the Tanba campaign began, Mitsuhide was a mid-ranking Oda retainer. By the time it ended in 1579 he was the senior corps commander at the top of Nobunaga's army and the daimyō of a 290,000-koku domain.

Why Tanba Was Hard

Tanba was a terrain problem. Mountainous, divided into small basins each held by a kokujin warrior family, threaded by narrow passes that could not absorb a large army — it was the kind of country where the local defenders had every advantage. When Nobunaga ordered the campaign in 1575, Mitsuhide's first wall was Akai Naomasa at Kuroi Castle. Akai was trusted in the locality and knew his mountain fort cold. Hatano Hideharu, nominally allied with Mitsuhide, struck him from behind at the decisive moment. The first Kuroi siege in January 1576 collapsed and Mitsuhide retreated to Kyōto in defeat.

The Second Campaign

Mitsuhide came back in 1577. This time he refused to be hurried. He took three years to peel away the perimeter of Tanba castle by castle. He developed Kameyama Castle as his base and built the supply lines for sustained sieges. From late 1578 to June 1579 he starved out Hatano Hideharu at Yagami Castle in a fifteen-month investment. When the garrison reached the edge of starvation Hatano surrendered. Tradition says Mitsuhide had given his own mother as a hostage to guarantee Hatano's safety, that Nobunaga overruled him and crucified Hatano anyway, and that Mitsuhide's mother was killed in retaliation. The story is a central anecdote in the grudge theory of Honnō-ji, but the documentary evidence for it is thin. Two months later, in August 1579, Kuroi Castle fell to internal collusion and Tanba came fully under Mitsuhide's control.

What Tanba Earned Him

The reward was enormous. Nobunaga granted Mitsuhide 290,000 koku in Tanba including Kameyama, Fukuchiyama, and Kuroi castles. Mitsuhide remained the lord of Sakamoto Castle in Ōmi as well, bringing his combined holdings above 340,000 koku and placing him alongside Shibata Katsuie and Hashiba Hideyoshi as one of Nobunaga's three most powerful corps commanders. From 1579 to 1582 his position inside the Oda command was unambiguous. On the eve of Honnō-ji he had been ordered west to reinforce Hideyoshi at Bitchū-Takamatsu.

What Tanba Bequeathed

The campaign left Mitsuhide three things. First, the experience of long siege warfare and the logistical instincts that came with it. Second, Kameyama Castle as a strategic base — the thirteen thousand troops who marched on Honnō-ji left from there. Third, the highest-tier trust within the Oda command and an autonomous corps. The capacity to kill Nobunaga at Honnō-ji was a capacity Mitsuhide had built in Tanba. The decade that turned him into Nobunaga's most trusted commander was the decade that gave him the military room to kill that same Nobunaga. This is the central paradox of Honnō-ji.

"Mitsuhide pacified Tanba and made his seat at Kameyama."