Stories of the Japanese 00707 [Late Kamakura Period] The Shimotsuki Incident

As the conflict between Adachi Yasumori and Taira no Yoritsuna deepened day by day, Yasumori included a sentence in a newly issued decree stating,
“The Miuchibito must fulfill their service and etiquette to the Tokuso.”
While the content seems ordinary at first glance, it essentially meant, “The Miuchibito must not interfere with the official duties of the shogunate.” It was clearly intended as a check on Yoritsuna.
Yoritsuna, taking the check from Adachi Yasumori as a declaration of war, launched an armed struggle.
On November 17, in the 8th year of Koan (1285), Yoritsuna reported to Sadatoki,
“Adachi Yasumori’s son, Munekage (1259–1285), is aiming for the position of Shogun. He seems to be boasting that ‘since my great-grandfather Adachi Kagemori was the secret child of Minamoto no Yoritomo, I also have a right to inherit the Shogunate.’”
and obtained approval to strike down the father and son, Yasumori and Munekage.
Sensing something was wrong as Yoritsuna gathered troops and Kamakura became restless, Yasumori went to serve at Sadatoki’s residence around noon, but he was killed there.
The Adachi clan, having had their head killed, were enraged and raised an army, leading to fierce battles throughout Kamakura. However, the Adachi forces were defeated one after another by the ambushes of Yoritsuna’s side that had been lying in wait, and Yasumori’s son Munekage was also killed in action. It is said that in the end, over 500 of the Adachi forces were killed or driven to commit suicide. Because this conflict occurred in November, it is called the Shimotsuki Incident.
The impact of this incident spread as far as Kyushu. Yasumori’s second son, Adachi Morimune (?-1285), had been working on the defense of Kyushu to guard against the Yuan dynasty, but upon hearing that his clan had been killed, he was enraged and raised an army to overthrow Yoritsuna along with his ally, Shoni Kagesuke.
However, Shoni Kagesuke had long been in conflict with his older brother, Tsunesuke, over their territory, and Tsunesuke sided with Yoritsuna. Tsunesuke besieged and captured Kagesuke’s home castle, Iwato Castle (Nakagawa City, Fukuoka Prefecture), and both Adachi Morimune and Shoni Kagesuke were killed in battle. The Adachi clan was defeated in Kyushu as well, and Taira no Yoritsuna emerged victorious. This is called the Battle of Iwato.
Yoritsuna destroyed his greatest political enemy and came to possess the vast territories of the Adachi and Shoni clans. These were given to the gokenin (shogunal retainers) as rewards, which temporarily resolved their dissatisfaction.
The Kamakura Shogunate established an office called the “Chinzei Tandai” to oversee the territories in Kyushu, further strengthening its control over the region. However, this was not a fundamental solution and only succeeded in prolonging the life of the shogunate for a while.
From this point on, Taira no Yoritsuna gained absolute power, and there was no one left who could oppose him. The court noble Ogimachi Sanjo Sanemi (1264–?) wrote in his diary, “Sanemikyo-ki”:
“After the Jiro Nyudo was executed, that man held total control of the government, and beyond the fear of the people, there was nothing else.”
(After Yasumori was executed, Yoritsuna reached the height of tyranny, and everyone was so afraid that they could do nothing.)