16 August 1225 (Karoku 1, 11th day of the 7th month 嘉禄元年7月11日) – Death of Hōjō Masako 北条 政子, wife of Minamoto no Yoritomo, the 1st Kamakura shōgun. After her husband's death, she exercised considerable indirect power and dominated the government until her death, her power being so great that she was called the “ama-shōgun” (nun shōgun).
Masako was the oldest child of Hōjō Tokimasa. She was said to be quite tomboy, was instructed in horseback riding, hunting, fishing, and she ate with men rather than with the women of the household.
Her father was the ruler of Izu Province and was given responsibility for Yoritomo who had been exiled to Izu after being defeated in the Heiji Rebellion. While Tokimasa was away in Kyoto on service guard, Masako and Yoritomo fell in love. The story of their union is mentioned in a section in Soga Monogatari called “Yumekai”.
Tokimasa opposed to their relationship and, fearing the Taira clan reaction, he ordered Masako to marry someone else, but she refused. It is said that she walked over a mountain to escape with Yoritomo and the couple was sheltered at Izusan Gongen (Izusan-jinja Shrine). Masako was 21 years old at the time. The power of the priesthood at Izusan was so strong that even her betrothed could not force his way in. Not long after, Masako gave birth to her first daughter, Ō-hime. Tokimasa finally accepted their marriage and the Hojo family became important supporters of Yoritomo. As Yoritomo's wife, she participated in the government administration and eventually became a representation of power for men of the Hōjō clan.
In 1180, Prince Mochihito, son of Cloistered Emperor Go-Shirakawa, planned to overthrow the Taira regime and called all the Minamoto clans spread throughout the various provinces to join.
Meanwhile at the beginning of 1182, Masako gave birth to a son, Minamoto no Yoriie. During her pregnancy, Yoritomo took a liking on Kame no Mae, moving her closer to him and visiting her often. Hearing about this, Masako was enraged and ordered Maki Munechika to destroy Fushimi Hirotsuna’s residence, where Kame no Mae lived. Yoritomo was enraged and after questioning Munechika, disgraced him by ordering him to cut off his top-knot with his own hands. Angered by Yoritomo's deed, Tokimasa returned to Izu with his warriors. Masako's anger, however, did not subside, and she sentenced Hirotsuna to exile in Totomi Province.
Masako's jealousy was unusual in this age of polygamy. Male aristocrats at the time had many mistresses, moving from one to another, a custom powerful samurai families followed in order to increase the population of the clan. Masako's father, Tokimasa, too, had several mistresses, and Masako had several siblings born to different mothers. Yoritomo had affairs with many women in his lifetime, although out of fear of Masako's jealousy, he did his best to hide them.
In 1183, Yoritomo agreed to make peace with his rival, Minamoto no Yoshinaka, on the condition that Yorinaka's son, Minamoto no Yoshitaka, marry his eldest daughter, Ō-hime. Under this pretext, Yoshitaka was ordered to Kamakura, where he was effectively held as a hostage. However the truce only last for a year and Yoritomo ordered Tonai Mitsuzumi to kill Yoshikata. Devastated by Yoshitaka's death, Ō-hime fell ill. Masako was enraged about the execution, blaming it for causing Ō-hime's illness; and Yoritomo was forced to kill Mitsuzumi, whose head was then displayed in public.
Although Mochihito’s plan had failed (he was later killed), with the support of the Hōjō clan and Masako, Yoritomo raised his army and began the Genpei War, the final war between the Minamoto and Taira clans. While his half brothers, Noriyori and Yoshitsune, were fighting against the Taira clan, Yoritomo continued his rule in Kamakura, and Masako always accompanied during his campaign. In 1185, Yoshitsune overthrew the Taira clan at the Battle of Dan-no-ura.
After the fall of the Taira clan, Yoritomo and Yoshitsune became enemies, and Yoshitsune, failing to gather an army, left Kyoto with his vassals, wife and mistresses. In 1186, Yoshitsune's favourite mistress, Shizuka-gozen, was captured and sent to Kamakura. Masako wished to see Shizuka perform the traditional Shirabyōshi dance, and Shizuka reluctantly did so. During the dance, she recited a poem that spoke of her love for Yoshitsune. This angered Yoritomo but Masako, remembering how she felt when she first met Yoritomo, was sympathetic so she calmed Yoritomo's anger and Shizuka’s life was spared.
In 1192, Yoritomo was named shōgun by Go-Shirakawa, who died later that year. That same year, Masako and Yoritomo had another son, Minamoto no Sanetomo. During her pregnancy, Yoritomo’s mistress, Daishin no Tsubone, gave birth to a boy named Jyogyo; however, fearing Masako's anger, no birth ceremony was held. Fearing Masako's jealousy, Daishin no Tsubone hid herself, and the boy was raised in hiding, without a wet nurse. At the age of 7, Jyogyo was sent to Ninna-ji Temple to become a monk, and Yoritomo secretly came to see him off.
In 1193, Yoritomo held a huge Makigari (hunt) at the foot of Mt. Fuji where Yoriie managed to kill a deer. Proud of his son’s achievement, Yoritomo sent a messenger to Masako which she replied back by saying, “No need to make a fuss over a samurai's heir killing a deer.”
In 1195, Masako traveled with Yoritomo to Kyoto to discussed marriage between Ō-hime and Emperor Go-Toba. Yoritomo wanted this marriage for the political advantage it would bring, and Masako thought that marriage ito the Imperial family would make Ō-hime happy, but she became very ill and died two years later. According to "Jokyuki," Masako grieved so deeply that she wanted to kill herself, but Yoritomo stopped her, saying that her death would make Ō-hime's afterlife worse.
Yoritomo died after a fall from a horse in 1199 and his son, Yoriie, succeeded him. Masako became nun but she didn’t take up residency in the monastery and still involved herself in politics. Along with her father Tokimasa and her brother Yoshitoki, Masako created a council of regents for the 18-year-old Yoriie.
There had been number of incidents in which Yoriie had misgoverned, increasing his retainers' discontent. Furthermore, Yoriie appointed his wet nurse's husband, Hiki Yoshikazu, to an important position and when Yoshikazu's daughter gave birth to Yoriie's first son, Minamoto no Ichiman, it placed Yoshikazu in a position of power. The rise of the Hiki clan was a threat to the Hōjō clan.
In 1203, Yoriie fell ill. Masako and Tokimasa decided to divide Japan in two by splitting power between Ichiman and Sanetomo. Unhappy with this decision, Yoshikazu appealed to Yoriie to intervene in this decision and Yoriie ordered the subjugation of the Hōjō clan. Hearing the plan, Masako sent messenger to Tokimasa, who then plotted to kill Yoshikazu. Ichiman died along with the Hiki clan in what became known as the Conspiracy of Hiki Yoshikazu.
Recovering from his illness, Yoriie retaliated but by then, full power was in the hands of the Hojo clan and, on Masako's orders, Yoriie was removed from the position of shōgun, forced to join the priesthood and confined to Shuzen-ji Temple in Izu. Yoriie was later assassinated. To avoid future problems, Masako put Yoriie's other children into the priesthood. One of them, Kugyō, became the head (betto) of Tsurugaoka Hachiman-gu Shrine.
Sanetomo was made shōgun with Tokimasa as his shikken (regent). In 1205, Tokimasa plotted to overthrow Sanetomo and replace him with his son-in-law, Hiraga Tomomasa. Masako and Yoshitoki, her brother and Tokimasa’s heir, foiled the plot. They forced Tokimasa into exile as a priest in Izu. Thereafter, Yoshitoki was placed in power as regent (the Maki incident).
In 1219, Sanetomo was killed by his nephew, Kugyō, when he made a visit to Tsurugaoka Hachiman-gu Shrine. Since Sanetomo died without an heir, Masako sent a messenger to Kyoto to express her wish to have one of the Retired Emperor Go-Toba's son to be sent to Kamakura to become shōgun, but Go-Toba refused. Masako and Yoshitoki abandoned the idea of installing an Imperial shōgun and decided to put Mitora (Fujiwara no Yoritsune), from one of the five Sekkan (regent) families, into power. Since he was only 2 years old, Masako was appointed his guardian and ruled the country in his place until her death in 1225.
Since Yoritomo's death in 1199, quarrels for supremacy started between the Kamakura Bakufu and the Imperial court in Kyoto. Those quarrels ended in the Jōkyū War in 1221 when Kamakura defeated the Imperial army in Kyoto, and the Hōjō regents in Kamakura achieved complete control over Japan. By redistributing the land they’d gained after the war, they were able to achieve loyalty among all the powerful people throughout the country. The emperor and the remaining governmental offices in Kyoto lost practically all effective power.
In 1232 a legal code, the Joei Shikimoku, was promulgated. It stressed Confucian values such as the importance of loyalty to the master, and generally attempted to suppress a decline of morals and discipline. Tight control was maintained by the Hōjō clan, and any signs of rebellions were destroyed immediately. The shōgun stayed in Kamakura without much power while deputies of him were located in Kyoto and Western Japan. Stewards and constables controlled the provinces tightly and loyally. The Hojo regents dominated the Kamakura Shogunate and were able to bring several decades of peace and economic expansion to the country until their downfall in 1333 when an external power began to threaten Japan.
Further reading:
https://www.newworldencyclopedia.org/entry/Hojo_Masako
https://en.wikipedia.org/wiki/Hōjō_Masako
Butler, Kenneth B. "Woman of Power Behind the Kamakura Bakufu," in Great Historical Figures of Japan. Murakami Hyoe and Thomas J. Harper, eds. Tokyo: Japan Cultural Institute, 1978