Sakuma Nobumori (佐久間 信盛, 1528-18 February 1582), also named Dewa no Suke (出羽介) and Uemon no Jo (右衛門尉), was a vassal of the Oda clan. Oda Nobunaga's banishment of Nobumori to Mount Kōya is widely seen as a symbol of Nobunaga's cruelty, even against his oldest servants, and one that highlights his shortcomings as a military commander.
Born in the Aichi District of Owari Province (nowadays Minami-ku Ward in Nagoya) and in the service of Oda Nobuhide, Sakuma was given custody of the young Oda Nobunaga.
Unlike other vassals whose loyalty fluctuates between Nobunaga and Oda Nobuyuki as clan chief, Sakuma remained resolutely attached to Nobunaga and fought constantly for him. Considered as the most important of Nobunaga's retainers, he is always available for every important battle under the command of his lord.
Sakuma is called "Noki Sakuma" (退き佐久間), which literally means "Sakuma who retreats" because of his careful tactics. He was successful in the campaign against the Rokkaku clan and helped put down revolts caused by Buddhist sects in Echizen province and Nagashima in Osaka.
In 1572, his unit of 3,000 men was part of the reinforcements sent by Nobunaga to help the 8,000 or so soldiers of Tokugawa Ieyasu against the 27,000 men led by Takeda Shingen. At the battle of Mikatagahara, Sakuma retreated after a previous engagement.
His companion, the commander Hirate Hirohide, however, who fought alongside Tokugawa's troops, lost his life and the conflict ended in a crushing defeat for the Tokugawa-Oda alliance.
In 1576, after the death of Harada Naomasa during the campaign against the heavily fortified and well supplied Hongan-ji temple in Osaka, Sakuma was chosen to replace Harada as commander and received troops from seven provinces, which put him at the head of the largest army of the Oda clan among the Oda vassals.
However, unlike his colleagues Akechi Mitsuhide, Shibata Katsuie or Hashiba Hideyoshi who all won battles on the fronts to which they were assigned, Nobumori made no progress against the Buddhist fanatics. After ten years of war, Nobunaga obtained a truce from the emperor to end the conflict in 1580.
That same year, Nobunaga wrote a document containing a fifteen point accusation against Sakuma, including his past failures with those encountered against the Hongan-ji.
Nobunaga banished Sakuma and his son Sakuma Nobuhide to the temple of Mount Koyasan where they were forced to spend their days in the manner of monks. Sakuma died in 1581 in Totsugawa in Yamato province. He is posthumously named Doumu Keigan (洞無桂巌) and Souyu (宗佑).
Nobumori's banishment is widely seen as representative of Nobunaga's cold-blooded treatment of even his oldest vassals and highlights his shortcomings as a clan leader as a military commander.
Nobumori, however, held frequent tea meetings and seemed more interested in them than in focusing on military affairs. After all, he never devised any comprehensive military measures against the members of Hongan-ji, even though their war remained in a stalemate. It was also noted that since childhood, Nobumori openly criticized Nobunaga.