During the Kamakura shogunate the Mōri were a gokenin family due to the fame of their ancestor Ōe no Hiromoto. Mōri Suemitsu, the fourth son of Ōe no Hiromoto inherited Mōri-shōen from his father and that is why he began to use the name. It is reasonable to say he is the first head of the Mōri clan but in the Mōri family tradition he is the 39th head of the family as he is the 39th linear descendant of Amenohohi-no-mikoto (天穂日命), an ancient god of Japan.[6] After the third head of the clan, Mōri Tokichika, his son Mōri Sadachika (毛利貞親) was supposed to succeed him but he and his son were both killed by the Hōjō clan and the great-grandson of Tsunemitsu became the next head of the clan.[7]
At the end of the Kamakura shogunate, they became distant from the shogunate and showed a favorable attitude to Ashikaga Takauji.[8]
Sengoku period
In the Sengoku period, Mōri Motonari expanded their power to the whole of Aki province and then to other neighboring provinces. In his generation, Mōri became the daimyō from a local jizamurai.[citation needed]
During the war with the Oda clan and the Ikkō-ikki, the Mōri helped the Ikkō-ikki clans by establishing a naval trade route between each other's provincial docks and harbours, the Oda eventually nullified this by laying siege to the trade ships between the two clans and went to further disrupt trade by attempting to destroy the Mōri fleet, failing on their first attempt in 1571. The second battle took place in 1579 with the Oda sending eight Atakebune (heavily armoured ships with iron-clad plating) warships to finally destroy the Mōri naval threat.
After a struggle between Toyotomi Hideyoshi, who led his army as a general of Oda Nobunaga, the two sides made peace and Mōri remained as a daimyō who kept six provinces in Chūgoku.
Edo period
In 1600, Mōri Terumoto nominally led the Western Army in the Battle of Sekigahara. The Western Army lost the battle and the Mōri clan lost four eastern provinces and moved their capital from Hiroshima to present-day Hagi, Yamaguchi. The newer fief, Mōri han, consisted of two provinces: Nagato Province and Suō Province. Derived from the former, Mōri han was referred to often as Chōshū han.
Mōri Motonari (毛利元就, 1497–1571), arguably the most famous member of the clan. Expanded the clan's power to nearly all of the Chūgoku region.
Mōri Takamoto (毛利隆元, 1523–1563), became head of the clan when his father "retired" but died young before his father, suspected assassination by poisoning.