The was a Japanese samurai clan of the Sengoku period (1467âÂÂ1573) and early Edo period (1603âÂÂ1868). The clan ruled Awa Province as a Sengoku daimyà  and was a major military power in the Kantà  region during the wars of the Nanboku-chà  period. Although confirmed as daimyà  of Tateyama Domain by the Tokugawa shogunate.
The Satomi claimed descent from the Seiwa Genji clan via Nitta Yoshishige (d. 1202), whose son Yoshitoshi took "Satomi" as his surname.
After the fall of the Kamakura shogunate in 1333, the Kantà  region was high unstable due to incessant conflict between the Kantà  kubà  under Ashikaga Shigeuji based in Kamakura and the Ashikaga shogunate, represented by the Kantà  Kanrei under Uesugi Noritada. The minor lords of Awa Province (present-day southern Chiba Prefecture ) were loyal to the Kanrei, but geographically, the province was very near Kamakura, separated only by the narrow Uraga Channel. To seize Awa Province, the Kantà  kubà  sent the Satomi clan under Satomi Yoshizane (1412-1488), who landed at Shirahama from which he gradually expanded to conquer the province. Satomi Yoshizane claimed to be the chieftain of the Satomi clan, but his ancestry is somewhat uncertain. His descendants are known as at the "Awa Satomi clan", and cadet branches of the clan existed in Dewa, Echigo, and Mino Province.
In 1516, Odawara-based Hà Âjà  clan defeated the Miura clan and seized Miura Peninsula, opposite of Uraga Channel from Awa Province. Furthermore, the Hà Âjà  expanded northward along Tokyo Bay, capturing Edo Castle by 1524. This threatened the Satomi clan from west and north. In response, Satomi Yoshitoyo launched an amphibious invasion of Kamakura, in the process of which his forces burned down the famed Shinto shrine of Tsurugaoka Hachiman-gu. This was a massive loss of prestige for Yoshitoyo, and led to an internal conflict within the Satomi clan. Satomi Sanetaka, head of a cadet branch of the clan attempted a coup d'état with Hà Âjà  assistance in 1533, but the attempt failed and he was killed. Yoshitoyo then attacked Sanetaka's son, Satomi Yoshitaka, but Yoshitaka escaped and together with the Hà Âjà  and a strong navy, he managed to drive out Yoshitoyo and seize power the following year. He then broke his alliance with the Hà Âjà  and revived the ancient feud between the clans. Soon afterwards, Satomi Yoshitaka seized Kazusa Province and from his base at Kururi Castle turned his attention to Shimà Âsa Province. Meanwhile, the Hà Âjà  has taken control of Musashi Province to the north of Shimà Âsa. The Hà Âjà  were far stronger, and their armies broke the Satomi forces and even attacked Kururi Castle, but Yoshitaka turned to Uesugi Kenshin for assistance and kept his independence. After his death in 1574, Uesugi Kenshin lost all of his territories in the Kantà  region and could no longer assist the Satomi. Yoshitaka's son, Satomi Yoshihiro (1530-1578) pledged fealty to Hà Âjà  Ujitsuna in 1539 and surrendered the northern half of Kazusa Province. The Satomi were involved in the First Battle of Kà Ânodai (1538) and the Second Battle of Kà Ânodai (1564). After his death to illness in 1578, a conflict arose between his son, Satomi Yoshishige and his younger brother, Satomi Yoshiyori. Yoshiyori had the support of the Hà Âjà  and defeated Yoshishige, but the clan was severely weakened. In order to better control commerce and to make better use of their maritime power, he relocated his seat from Kururi to Okamoto Castle.
By 1580, as the situation for clan improved, he built Tateyama Castle. In 1590, Toyotomi Hideyoshi launched a campaign to destroy the Hà Âjà Â. Satomi Yoshiyasu quickly attacked the Hà Âjà  strongholds in Kazusa in an arbitrary attempt to recover his former territories. However, as these attacks took place without Hideyoshi's permission or coordination with Toyotomi generals, Hideyoshi was angered, and he subsequently reduced the Satomi clan's holding to only Awa Province. Yoshiyasu relocated his seat from Okamoto to Tateyama Castle. At the beginning of the Edo period the clan was named the daimyà  of Awa Province with a kokudaka of 120,000 koku under the Tokugawa shogunate. However, the clan was implicated in the à Âkubo Nagayasu Incident of 1614, and Satomi Tadayoshi (1594âÂÂ1622) was banished to Hà Âki Province (present-day Tottori Prefecture), and had his holdings reduced to 30,000 koku. Tadayoshi had no heir, and the clan died out with his death.
In 2012, the ruins of two early castles in southern Bà Âsà  Peninsula, Inamura Castle and Okamoto Castle were collectively designated a National Historic Site under the name .
The original Tateyama Castle was allowed to fall into ruins upon the attainder of Tateyama Domain in the death of Satomi Tadayoshi in 1622. Although the domain was restored in 1781 under Inaba Masaaki, he was not permitted to rebuild the castle, but only to construct a jinya fortified residence. The current tenshu is a 1982 reconstruction intended to boost local tourism and to function as an annex to the local Tateyama City Museum.