<論説>戦国大名尼子氏権力の形成 : 出雲国奉公衆塩冶氏の掌握と討滅

Abstract

鎌倉期守護の系譜を引く室町期塩冶氏は、その基盤である出雲国最大の河川水運の要衝を確保して、特に出雲国西部において強大な政治的実力を有し、十五世紀末には杵築大社両国造家など周辺諸領主と結集して、自立性の極めて強い地域秩序形成を企図している。しかも塩冶氏は幕府奉公衆を務めており、京極氏の守護権がほとんど及びえない存在として、出雲国内において最も特徴的な位置を占めていたと言える。尼子経久は、このような性格と動向を示す塩冶氏について、十六世紀のかなり早い段階で実子興久に家督を継がせ、やがてこれを武力討滅することにより、その権力基盤と歴史的性格の大部分を継承し、一国支配権の確立に不可欠な出雲国西部における権力の浸透を実現している。本稿においては、大名としての尼子氏権力形成過程における最大の画期であると考えられるにもかかわらず、従来非常に軽視されてきた塩冶氏掌握の歴史的意義を明らかにしていきたい。

The main purpose of this paper is to make clear how important it was for the Amago to eliminate their rivals within Izumo 出雲 province, the Enya, on their way to becoming daimyo. Concerning the historical characteristics of the Enya in the Muromachi period we can indicate three main points : First, the Enya were the most powerful in the western part of Izumo. Their position was based on the financial strength derived from the area under their rule, which was located at a strategic location for river transportation in Izumo. Second, because the Enya were members of the hokoshu 奉公衆, the direct army of the shogun, they were thus independent of the authority of the shugo of the province, the Kyogoku 京極 family. So even after the Amago succeeded to the estate and the authority of the Kyogoku, they were unable to thereby control the Enya. Third, at the close of the fifteenth century, the Enya were allied with other adjacent lords (kokujin) against the Muromachi shogunate. This military alliance was a great force within the province and aimed at establishing an independent local order. Thus the most important problem facing the Amago at the close of the fifteenth century was how to eliminate the Enya and bring the entire province of Izumo under their control. The process was begun early in the sixteenth century when Amago Tsunehisa 尼子経久 made his son Okihisa 興久 the heir to the Enya, and completed in the 1530s when the Enya were wiped out by military force. The Amago succeeded to the Enya power base in western Izumo and to their connection with the neighboring kokujin. This was the crucial step in bringing the entire province of Izumo under Amago control.