He was born the third son of
Sanada Yukitaka in 1547, but the exact date is unknown. His childhood name was Gengorō (源五郎). At birth, he had no right to succeed his father because of his two older brothers,
Nobutsuna and Masateru. In 1553, at seven years old, he was sent to the Takeda clan's headquarters in Kai as a hostage. There he becomes part of the
Okukinjūshū (奥近習衆), a group of six young servants close to
Takeda Shingen. According to the
Kōyō Gunkan, Shingen favoured him as he soon recognized that Masayuki's talents and insight rivaled those of his father Yukitaka. As such, he is sometimes included among the
Twenty Four Generals, alongside his father and two older brothers. In 1558, he became the foster son of the Mutō family, a branch of the Ōi clan, of which Shingen's mother descended from, and adopted the name Mutō Kihei (武藤喜兵衛).
Service under Takeda Towards 1564, he married Yamanote-dono (山手殿), a daughter of Uda Yoritada, who was a local lord of
Tōtōmi Province. Later she gave birth to his two sons
Nobuyuki and
Nobushige. During this period, he participated in many battles under the Takeda clan, including the
Fourth Battle of Kawanakajima (1561) and the
Battle of Mimasetōge (1569). Also most importantly, from 1572 onwards, he joined Shingen in his campaign towards Kyoto against the
Oda and Tokugawa clans and took part in the
Battle of Mikatagahara (1573). In May 1573, Shingen died amidst his campaign and so Masayuki continued to serve his heir
Takeda Katsuyori. In 1574, his father
Yukitaka died. At that point, his eldest brother
Sanada Nobutsuna had already succeeded his father as the head of the Sanada clan. However, during the disastrous
Battle of Nagashino (1575) against the
Oda clan, both his older brothers, Nobutsuna and Masateru, were killed, so he came back to Sanada clan and claimed his inheritance. In this, Masayuki supposedly had the support of
Kōsaka Masanobu, who held Kaizu Castle in Northern
Shinano and was also a chief retainer of the Takeda clan. Katsuyori accepted his claim without any qualms. In 1579, a year after
Uesugi Kenshin's death, an alliance between the Takeda and Uesugi clans was established. The following year, ordered by Takeda Katsuyori, Masayuki invaded western
Kōzuke, which was a
Hōjō domain at the time, and seized
Numata Castle, putting it under control of the Takeda clan. The same year, he was appointed the title of
Awa-no-kami (従五位下・安房守). In 1581, he was ordered by Katsuyori to supervise the construction of the new Shinpu Castle at
Nirasaki. In the same year, Numata Kageyoshi, former lord of Numata Castle, attempted to retake his old fief, but Masayuki schemed to assassinate him and thwarted his plans. In April 1582, Oda and Tokugawa allied forces started an invasion of the Takeda territory. It is said that Masayuki had intended to shelter Katsuyori and advised him to abandon
Kai Province and flee towards Sanada's domain in Kōzuke(
Iwabitsu Castle). Instead, Katsuyori decided to take shelter at
Oyamada Nobushige's Iwadono Castle, but was betrayed and ultimately died at
Tenmokuzan. After the fall of the Takeda clan, Masayuki yielded to
Oda Nobunaga and was put under the orders of one of Nobunaga's chief commanders,
Takigawa Kazumasu. Masayuki managed to retain most of his domain, but had to abdicate Numata Castle to Takigawa Masushigue, Kazumasu's relative.
Tenshō-Jingo Conflict However, Nobunaga soon died at the
Incident at Honnō-ji on June 21, 1582. Upon Nobunaga's death, Oda clan's grasp over former Takeda territories weakened. Amidst the chaos, Oda retainers who were assigned by Nobunaga to govern those territories, such as
Mori Nagayoshi and
Kawajiri Hidetaka amongst others, either fled or were killed by local insurrection. After the chaos following the death of Nobunaga, Tokugawa Ieyasu invaded Kai and Shinano province to establish control there on the consent from senior vassals of
Oda clan. However, at the same time,
Uesugi clan and the
Hōjō clan also aspired to seize the vast area in
Shinano Province,
Kōzuke Province, and
Kai Province (currently Gunma Prefecture), which ruled by the remnants of the many small clans formerly serving Takeda clan. following of disorder post death of Nobunaga, at the same time with Ieyasu departure an army of 8,000 soldiers to those disputed region. This caused the triangle conflict between those three factions in the event which dubbed by historians as broke out. On June 13, the Hōjō clan had captured Iwadono Castle in Tsuru District, and instructed Watanabe Shozaemon, a local magnate from Tsuru District to assist them in their conquest. Subsequently, Sanada Masayuki led his army and received
Numata Castle to the Uesugi clan. On July 9, Masayuki changed his allegiance from the Uesugi clan to the Hōjō, he surrendered to Hōjō Ujinao. On July 5, Takigawa Kazumasu lost decisively against the invading Hōjō army at the
Battle of Kannagawa. In that occasion, Masayuki actually escorted back Kazumasu's remaining forces through
Suwa, in Shinano. Though, seeing this chance, Masayuki sent his uncle Yazawa Yoritsuna and took back
Numata Castle. Also, he put his oldest son Nobuyuki in charge of
Iwabitsu Castle, further reinforcing eastern Kōzuke. On July 10,
Uesugi Kagekatsu invaded Northern Shinano. Masayuki sided with the Uesugi initially, but a couple of weeks later he defected to Hōjō's side. Both Uesugi and Hōjō's armies came to face each other at Kawanakajima on July 30, but direct combat was avoided as the Hōjō army turned back and advanced south towards Kai province, which was in turn invaded by Tokugawa forces. Meanwhile, one of Uesugi clan's major retainer, Shibata Shigeie, revolted and Uesugi's forces also had to turn back from Northern Shinano to deal with it. On July 12 as the troops under
Hōjō Ujinao advanced across Usui Pass, Nobushige resisted them, abandoned the
Komoro Castle, and retreated to a fortress which he deemed more suitable to defend against the Hōjō army. On October 19, Sanada Masayuki suddenly changed his allegiance again as now he helped the Tokugawa clan by attacking Nezu Masatsuna, a lieutenant of Hōjō Ujinao, and cooperating with Yoda Nobushige to resist the Hōjō clan forces around Komoro, as Ieyasu has instructed Masayuki. It was believed by historian that the Information about Masayuki's defection have reached the Hōjō clan in early October. In response for Masayuki betrayal, a commander of Hōjō forces named Fujita Ujikuni tried to capture Numata castle. However, he failed to do so as Masayuki resisted his attempt.
Conflict with Tokugawa In 1583, Masayuki started the construction of
Ueda Castle and the surrounding town. It became the headquarters of the Sanada clan in the following years. In 1584, Tokugawa Ieyasu lead his army west towards Owari province in the
Battle of Komaki and Nagakute against
Hashiba Hideyoshi. Masayuki was left in northern Shinano to keep the Uesugi clan in check and took this opportunity to subjugate small, neighboring landlords and consolidate his power in the region. In December, as Ieyasu made peace with Hideyoshi and returned to his territory, he was pressed by
Hōjō Ujinao to act on the terms of their treaty. In 1585, Masayuki moved their main bastion from
Sanada-shi Yakata to
Ueda Castle. In that treaty, among other terms,
Tokugawa Ieyasu agreed to transfer
Numata Castle and its adjacent lands in Kōzuke province to the Hōjō clan. In April 1585, Ieyasu advanced his army into Kai province in a move to pressure Masayuki into abdicating Numata Castle. Masayuki however, resisted having to hand it over, having conquered it with great effort years before. Ultimately, he decided to cut relations with Tokugawa Ieyasu and once more switched allegiances by sending his second son Nobushige to
Uesugi Kagekatsu as a hostage. With this move, he effectively joined
Hashiba Hideyoshi's side, which opposed the Tokugawa-Hōjō alliance. Months later, Tokugawa forces invaded Sanada clan's territory in northern Shinano province with 7,000 men and laid siege to Ueda Castle, which was defended by only 1,200 soldiers. However, Masayuki was able to inflict 1,300 casualties on Tokugawa's side and won a decisive victory. Meanwhile, Hōjō Ujinao attacked Numata Castle, but was also rebuffed by Sanada forces. This was the First Battle of Ueda Castle, a victory that earned Masayuki national prominence. Following this, Masayuki went from being just a former Takeda retainer to become recognized as an independent
daimyō. In 1586, after Ieyasu reconciled with Hideyoshi, He was given permission by Hideyoshi to attack Masayuki in Ueda. The reason of this allowance was because Masayuki did not even sent his family as hostages to Hideyoshi to symbolize his submission. However, as Masayuki immediately ask mediation of Kagekatsu to offer his surrender to the
Toyotomi clan, Hideyoshi recalled Ieyasu to abort his invasion. Then Masayuki followed by personally came to Kyoto to offer his official submission to Hideyoshi.
Service under Toyotomi Following his victory over the Tokugawa clan, Masayuki became a vassal to
Toyotomi Hideyoshi. In doing so, he sent his son Nobushige (at the time a hostage to Uesugi clan) as a hostage to
Osaka. In 1586, the Hōjō clan tried to take Numata Castle once more, but again were repelled. Tokugawa forces also gathered and marched towards Ueda Castle again, but Toyotomi Hideyoshi interposed. At this point, Hideyoshi's political presence in Japan was too strong for the Tokugawa clan to oppose, and at his mediation, the attack was called off. However, he also designated Masayuki as a back-up power to the bigger Tokugawa forces in the region. This effectively meant that Masayuki now responded to Tokugawa Ieyasu in all military matters. The following year, 1587, saw Masayuki travelling to
Sunpu to meet with Tokugawa Ieyasu. Then, he went to Osaka to be received in audience by Toyotomi Hideyoshi, and thus formally become a vassal of the Toyotomi regime. Two more years would pass until the dispute between the Sanada and Hōjō clans involving Numata Castle and adjacent areas would be mediated by Hideyoshi and resolved. In 1589, Hideyoshi decided the Sanada clan would relinquish all of its domain east of
Tone River, including Numata Castle, to the Hōjō clan. In turn, he granted them some territory in southern Shinano. However, by the end of that year, Inomata Kuninori, a retainer from the Hōjō clan who was now holding Numata Castle, was deceived into attacking the nearby
Nagurumi Castle, located west of Tone River and defended by Sanada forces. The attack was successful and the castle was seized by Hōjō forces, but by this time,
Toyotomi Hideyoshi had sanctioned a rule which prohibited
daimyōs from engaging in battle over private disputes. This incident fully breached this rule and it would go on to become the reason of the
Siege of Odawara in 1590, and the subsequent fall of the Hōjō clan.
Sekigahara campaign After Hideyoshi's death in 1598, Masayuki joined
Ishida Mitsunari's side during the
Battle of Sekigahara. Masayuki sent his eldest son, Nobuyuki, to the eastern side, while Masayuki and his younger son, Nobushige, fought on the western side, a move that ensured the Sanada clan's survival. Fortifying Ueda Castle, Masayuki fought against
Tokugawa Hidetada's 38,000 men with only 2,000 soldiers. This was the Second Battle of Ueda Castle, and, whilst it was not exactly a victory, Masayuki was able to deliver a heavy blow to Hidetada and delay his forces for long enough that they were unable to show up at the main battlefield on time. However, the western side, led by Ishida Mitsunari, lost the main battle, and the victorious Tokugawa Ieyasu was able to redistribute fiefs at will. Masayuki and Yukimura were initially going to be executed, but, given Nobuyuki's participation in the eastern army, they were instead exiled to
Kudoyama in
Kii province. The
Sanada clan was inherited by
Sanada Nobuyuki. During his time in exile, Masayuki received financial supports from Nobuyuki. According to the "Senko Jitsuroku" and other sources, he also received support from the Kishu Domain and Rengejoin Temple (Koyasan, Wakayama Prefecture), and was given 50 koku annually by the lord of the Kishu Domain,
Asano Nagaakira. A letter from Masayuki dated January 5th, states that Masachika (Masayuki's third son) sent 20 ryo of the windfall of 40 ryo. (in 2021, 20 ryo is equivalent to about 2 million yen as 1 ryo is equal of 100,000 yen). On March 15, 1603 (Keicho 8), Masayuki also a letter to Shinkoji Temple (Ueda City, Nagano Prefecture) ("Shinkoji Documents") to ask Tokugawa Ieyasu to seek pardon through
Honda Masanobu. In the postscript of the letter it is also written that Masayuki also felt grateful as Shinkoji Temple had sent him two momme (1,000 yen). Sanada Masayuki died of an illness in Kudoyama in 1611. ==Legacy==