The Naoe Letter: How One Letter Called Sekigahara Into Being

On April 14, 1600, a letter from the Uesugi reached Ieyasu. The signatory was the lord of 1,200,000-koku Aizu, Uesugi Kagekatsu; the actual author was Naoe Kanetsugu. Its purpose, on the surface, was to answer Ieyasu's charges that the Uesugi were preparing rebellion. Across sixteen articles it took up each charge in turn and rebutted it. Ieyasu read it as a declaration of war. The document is what later history calls the Naoejō.

What the Letter Said

The Naoejō argued three things. First, that the Uesugi's domestic activity — castle work, weapons procurement, the positioning of barriers — was the ordinary business of a daimyō newly installed in his territory, not rebellion. Second, that Ieyasu's grounds for ordering the Uesugi to Kyoto for an explanation were thin. Third, that the suspicions circulating around the Uesugi were caused by Ieyasu's own conduct and could not be resolved by Uesugi protestations of innocence. The logic was tight; the tone was uniformly defiant; the sixteenth article included a barbed remark about Ieyasu's own judgment. Ieyasu was furious, and in June he ordered the Aizu Expedition.

Coordination With Ishida Mitsunari

Recent scholarship no longer takes the Naoejō as Kanetsugu's unilateral provocation. In early 1600, Uesugi Kagekatsu, Ishida Mitsunari, and Naoe Kanetsugu were secretly developing a strategy to pin Ieyasu between an eastern and a western front. Draw Ieyasu out toward Aizu; while he was tied down in the east, Mitsunari would rise in the west. The Naoejō was very likely the trigger that strategy required. When Ieyasu marched east in July, Mitsunari raised his army at Ōsaka, and the Sekigahara configuration was set.

The Ironic Ending

The ending was ironic for Kagekatsu and Kanetsugu. The main engagement at Sekigahara on September 15 went to the Eastern Army, and the Uesugi were reduced from 1,200,000 koku at Aizu to 300,000 koku at Yonezawa. Kanetsugu, as a leading architect of the strategy, was open to liquidation, and the Tokugawa decision to reduce rather than destroy the Uesugi reveals deliberate political restraint. Kanetsugu spent the rest of his life rebuilding the reduced domain at Yonezawa and keeping the Uesugi house alive into the Edo period. The cost of the Naoejō, and the long work of repaying it, were both his.

"If that is your understanding of how the realm is to be governed, there is nothing further to be said."