Izumo Province

The old name of the eastern half of Shimane Prefecture. The lower reaches of rivers such as the Hii River and the Iinashi River, which flow into Lake Shinji and Lake Nakaumi, are alluvial plains, and the area has been rich in agricultural productivity since ancient times. As there are many myths set in Izumo, there is a theory that a rival power to the Yamato Imperial Court existed in the Izumo region before the Taika period, but at present this cannot be verified archaeologically.

According to the Izumo no Kuni Fudoki, compiled in 733 (Tenpyo 5), Izumo Province was made up of nine counties: Iou, Shimane, Aika, Tatenui, Izumo, Kandou, Iishi, Nita, and Ohara. However, after the Fudoki was published, Nogi counties were separated from Iou counties, making the total number of counties ten. Around the 8th century, the Izumo Kuni no Miyatsuko, who was the lord of Izumo County, was a powerful clan from the pre-Taika period whose ancestor was Amenohohi no Mikoto, and under the Ritsuryo system, he was also a county governor and was in charge of the rituals of the two major shrines of Kitsuki and Kumano. However, in 798 (Enryaku 17), he was prohibited from holding both roles as county governor and moved to Kitsuki (Taisha-cho, Izumo City) to focus on rituals. The provincial capital under the Ritsuryo system was located near Rokusho Shrine in Okusa-cho, Matsue City today.

During the Kamakura period, the shugo was appointed by the lineage of Sasaki Yoshikiyo, but Yoshikiyo's grandson Yoriyasu established his residence in Enya (Izumo City) and took the surname Enya. During the Nanboku-cho period, when the shugo Enya Takasada was overthrown, Kyogoku (Sasaki) Takauji (Doyo) became the shugo instead. The position was temporarily taken over by the Yamana clan, but after the Meitoku Rebellion (1391), it was returned to the Kyogoku clan, and the Amago clan, a member of the family, entered Toda Castle (Hirose-cho, Yasugi City) as the deputy shugo. Taking advantage of the Onin War (1467-1477), Amago Tsunehisa grew into a Sengoku daimyo by eliminating the shugo authority of Kyogoku Masatsune, and in the first half of the 16th century, he expanded his influence into the two provinces of San'in and San'yo. However, during the reign of Amago Yoshihisa, he was attacked by the Mori clan of Aki (Hiroshima Prefecture) and was destroyed in 1566 (Eiroku 9), and Izumo came under the control of the Mori.

After the Battle of Sekigahara, Horio Yoshiharu entered the area, built Matsue Castle, and moved his base from Hirose to Matsue. The Horio clan and the Kyogoku clan, who entered after him, both died out as they had no heirs. In 1638 (Kan'ei 15), Matsudaira Naomasa entered the area as lord with 186,000 koku of rice, and the Matsudaira clan continued to rule until the end of the Edo period. During that time, the area was divided into branch domains, Hirose with 30,000 koku and Mori with 10,000 koku. In 1871 (Meiji 4), the abolition of the feudal domains and the establishment of prefectures led to the creation of Matsue, Hirose, and Mori prefectures, but in November of the same year, these were merged and Oki was added to form Shimane Prefecture. After that, the area of ​​Shimane Prefecture changed, but in 1881 it became the three provinces of Izumo, Iwami, and Oki, which remains the case today.

[Da. T. Fujioka]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

島根県の東半部にあたる旧国名。宍道(しんじ)湖、中海(なかうみ)に流入する斐伊(ひい)川、飯梨(いいなし)川などの河川の下流域には沖積平野が開け、古代から農業生産力の豊かな土地であった。出雲を舞台とする神話が多く伝えられていることから、大化(たいか)前代の出雲地方に、大和(やまと)朝廷に拮抗(きっこう)する勢力が存在したのではないかとする説もあるが、現在のところ考古学的に実証することはできない。

　733年（天平5）撰進(せんしん)された『出雲国風土記(ふどき)』によると、出雲国は意宇(おう)、島根、秋鹿(あいか)、楯縫(たてぬい)、出雲、神門(かんど)、飯石(いいし)、仁多(にた)、大原の9郡から成り立っているが、『風土記』以後、意宇郡から能義(のぎ)郡が分立して10郡となった。8世紀ごろ意宇郡の大領であった出雲国造(くにのみやつこ)は、天穂日命(あめのほひのみこと)を祖先とする大化前代からの豪族で、律令(りつりょう)制下では郡司であるとともに、杵築(きづき)・熊野2大社の祭祀(さいし)をつかさどったが、798年（延暦17）郡司兼帯を禁じられ、杵築（出雲市大社町）に移って祭事に専念することになった。なお、律令制下の国府は今日の松江市大草町の六所(ろくしょ)神社付近にあった。

　鎌倉期の守護は佐々木義清(よしきよ)の系統が任じられたが、義清の孫頼泰(よりやす)は塩冶(えんや)（出雲市）に居を構えて塩冶姓を称した。南北朝期に入り、守護塩冶高貞(たかさだ)が失脚すると、かわって京極(きょうごく)（佐々木）高氏(たかうじ)（導誉(どうよ)）が守護となった。一時山名(やまな)氏に奪われたが、明徳(めいとく)の乱（1391）後、ふたたび京極氏に還補(げんぽ)され、守護代として一族の尼子(あまご)氏が富田(とだ)城（安来(やすぎ)市広瀬町）に入城した。尼子経久(つねひさ)は応仁(おうにん)の乱（1467～1477）を契機として、京極政経(まさつね)の守護権力を排除して戦国大名に成長し、16世紀前半には山陰・山陽2道に勢力を拡大した。しかし、尼子義久(よしひさ)の代に至って安芸(あき)（広島県）の毛利(もうり)氏の攻撃を受け、1566年（永禄9）滅亡し、以後出雲は毛利の支配下となった。

　関ヶ原の戦い後、堀尾吉晴(ほりおよしはる)が入国、松江城を築いて本拠を広瀬から松江に移した。堀尾氏とそのあと入部した京極氏は、ともに嗣子(しし)がなかったので断絶、1638年（寛永15）松平直政(なおまさ)が18万6000石の藩主として入部し、以後幕末まで松平氏の支配が続いた。その間、広瀬3万石、母里(もり)1万石の支藩を分出した。1871年（明治4）廃藩置県により松江、広瀬、母里の各県が誕生したが、同年11月これらを合併し、隠岐(おき)もあわせて島根県が成立した。その後、島根県域には変動があったが、1881年に旧出雲、石見(いわみ)、隠岐の3国域となり、現在に至っている。

［藤岡大拙］

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