456-year-old letter from warlord Motonari Mori to vassal discovered in Shizuoka

(Mainichi Japan) October 30, 2009

A letter thought to be from Motonari Mori, a major leader of the Sengoku period, to a major vassal has been found in a private home in Shizuoka Prefecture.

The letter dates from when Mori, based out of present day Hiroshima Prefecture, was making the transition into an expansionist lord. The letter names a vassal very little is known about, making it "a precious record for research into both Motonari and the history of the region," according to one researcher.

Mori (1497-1571) was born toward the end of the Muromachi period, and eventually took control of most of the Chugoku region in western Honshu, becoming one of the most powerful warlords of the mid-Sengoku period.

The letter, measuring 28.5 centimeters by 44 centimeters and dated Dec. 14, 1553, was found among the belongings of a deceased descendant of a vassal. Tatsuo Kamogawa, an associate professor of historiography at the University of Tokyo, concluded that the document was written by a private secretary on Mori's direction after analyzing the content and word usage. That the letter was signed on the left side of the page is also apparently characteristic of Mori.

The recipient was Mori's son-in-law and vassal Takaie Shishido. The letter instructs Shishido to relay the official endorsement of an ally named Yuki, in a village in the domain of Bingo -- present day northeastern Hiroshima Prefecture.

It had been known that Shishido had requested to bring Yuki under his jurisdiction, but the letter shows that Mori denied Shishido's request, instead seeking to bring Yuki into a direct vassal relationship with himself. The document also reveals that Yuki called on Mori to protect Yuki's rank and territory, and that Mori accepted these conditions. Furthermore, the letter reveals that Yuki was an important subordinate and ally of Mori.

"You can see in the letter that Mori was aggressively expanding his clout at that time," says Kamogawa.

Two years after the letter was sent, Mori defeated a vastly numerically superior army under warlord Harukata Sue at the battle of Itsukushima, beginning his rise in power and prominence.