Suō Province was in the Sanyōdō, or Sanyō Region, an area encompassing provinces in the western portion of Honshū along the Seto Inland Sea.
In current terms, Suō Province corresponds to the southeast half of Yamaguchi Prefecture. The province was comprised of six districts, including Ōshima, Kuga, Kumage, Tsuno, Saba, and Yoshiki. The provincial capital was in the city of Hōfu in the Saba District.
During the Sengoku period, the Ōuchi clan governed Suō and neighboring Nagato Province based in the city of Yamaguchi in Suō.
During the Kamakura period, Suō was ruled primarily by the Hōjō clan. Upon the fall of the Kamakura bakufu in 1333, Emperor Godaigo formed a new political administration known as the Kenmu no shinsei and, among other actions, appointed Washizu Nagahiro to serve as the shugo daimyō of Suō. Nagahiro was born into the Ōuchi family but changed his name to Washizu after becoming the designated successor to the head of his wife’s family. Godaigo attempted to restore the authority of the Court, but these actions upset the military class that formed the base of his support, and, in 1336, Ashikaga Takauji from the Kawachi-Genji clan rebelled and the new administration collapsed. The Ōuchi then allied themselves with Takauji as the new supreme ruler. In 1336, Nagahiro headed east from Suō to ally himself with Takauji after Kyōto had been taken over by Kitabatake Akiie, battling against forces loyal to Godaigo. Nagahiro governed Suō as a sōryō, or regional landholding of the Ōuchi. The Ōuchi governed Suō for over two centuries, from 1334 to 1551.
1465-1495: Ōuchi Masahiro
1495-1528: Ōuchi Yoshioki
1528-1551: Ōuchi Yoshitaka
- Ōuchi clan
- Sue clan
- Mōri clan
1551: Taineiji no hen – the Tainei Temple Incident in which a senior retainer named Sue Harukata rebelled against his lord, Ōuchi Yoshitaka, caausing Yoshitaka to take his own life in the Tainei Temple in Nagato Province
1555-1557: Bōchō keiryaku – an invasion by Mōri Motonari of Aki Province into the Ōuchi-controlled provinces of Suō and Nagato that led to the demise of the Ōuchi clan
1569: Ōuchi Teruhiro no ran – a revolt led by Ōuchi Terumoto and former retainers of the Ōuchi against the Mōri based on grievances against their new lord
Tamano-oya Shrine: In 1494, Tamano-oya was the first shrine visited by Ōuchi Yoshioki when he made a round of visits to five shrines in Suō to announce his victories in battle in Kyūshū.
Nikabe Shrine: Built in the ninth century and referred to as the third shrine. In 1494, Nikabe was the third shrine visited by Ōuchi Yoshioki when he made a round of visits to five shrines in Suō to announce his victories in battle in Kyūshū.
Iwaki Shrine: Originally, built in the sixth century, the main hall was constructed by Ōuchi Masahiro in 1469, and has design features reminiscent of the Muromachi period.