The Northern House of the Fujiwara clan (藤原北家)
The Northern House of the Fujiwara clan was a family line whose originator was FUJIWARA no Fusasaki, the second son of FUJIWARA no Fuhito, the minister of the right. It was one of four Fujiwara families. The name came from the fact that the house of FUJIWARA no Fusasaki was located north of the house of his elder brother, FUJIWARA no Muchimaro.
Summary
The originator, Fusasaki, was promoted to councilor first among four Fujiwara brothers during the era of Emperor Gensho, later became the first Naishin (government post) since his grandfather, FUJIWARA no Kamatari, and fought as an aide close to the Emperor Gensho for political power against Nagayao. During the era of Emperor Shomu, Fusasaki gained political power after the Nagayao no Hen (Conspiracy of Nagayao) in 729 and controlled the political power as a pivotal figure, particularly among the political power by the four Fujiwara brothers, but he died in 737 together with other brothers due to the spread of smallpox.
Thereafter, from the late Nara period through the early Heian period the Northern House of the Fujiwara clan had been losing ground to the Southern House of the Fujiwara clan and the Ceremonial House of the Fujiwara clan, partly because although Fusasaki's sons, FUJIWARA no Nagate and FUJIWARA no Uona, became ministers of the left in the era of Emperor Konin, Nagate's heir, FUJIWARA no Oyori, died young and Uona was involved in HIKAMI no Kawatsugu's war, whereupon he fell from power.
However, since the era of Emperor Heijo, FUJIWARA no Fuyutsugu (who had won the confidence of Emperor Saga) had rapidly gained power and started to overwhelm other families when the Southern House lost its power after the {Iyo Shinno no Hen} (Conspiracy of Imperial Prince Iyo) of 807, and the Ceremonial House lost its power after the Kusuko no Hen Conspiracy of 810. Moreover, the main branch of the Northern House became maternal grandfather over three generations--Fuyutsugu (Emperor Montoku), FUJIWARA no Yoshifusa (Emperor Seiwa) and FUJIWARA no Mototsune (Emperor Suzaku and Emperor Murakami)--whereby the predominance of the Northern House was established. Subsequently, the main branch of the Northern House became the leader of Toshi/Toji, and produced regents and chief advisors to the Emperor. Later, in the generations of FUJIWARA no Michinaga and FUJIWARA no Yorimichi, the government of Fujiwara's Sekkan (regent to the Emperor) reached full bloom.
The descendant of Michinaga and Yorimichi produced Sekke (the Setsu Family) to finally dominate the highest rank of kakaku (family status) among the court nobility. Most of the Dojo Family, which is another family line that used the Fujiwara cognomen, also descended from the Northern House.
The derivative clan was not merely limited to court nobility but also included a large number of samurai families that had influence mainly in Kanto, Hokuriku and Tohoku, claiming to be descended from the Northern House--such as the FUJIWARA no Michikane-Utsunomiya clan, the Oda clan, the FUJIWARA no Nagaie-Nasu clan, the Uesugi clan of the Kajuji group, the Fujiwara-Yamakage-Date clan, the FUJIWARA no Toshihito-Saito clan, the Kato clan, the FUJIWARA no Hidesato-Oshu Fujiwara clan, the Ashikaga clan (the Fujiwara clan), the Oyama clan, the Yuki clan, the Sano clan and the Onosaki clan.
Although the Northern House was the last of the four Fujiwara families to successfully flourish, as a result it spread the most extensive roots among the four Fujiwara families.