The Jinshin War (壬申の乱)
The Jinshin War was the biggest domestic war in ancient Japan and broke out in 672 and Emperor Tenchi's younger brother, Prince Oama (later Emperor Tenmu) launched a revolt taking powerful local clans on his side against Prince Otomo (given the name Emperor Kobun later in 1870) who was a son of Emperor Tenchi. It was a rare domestic war in that the insurgent Prince Oama won. The year 672 corresponding to Jinshin (ninth year of the sixty-year Chinese calendrical cycle) so it was called the Jinshin War.
Also this war was a battle over the imperial throne so before the Second World War, if the students did not advance to the old-education-system high school or more, they were not educated about this war.
Progress of the War
In the late 660s, Emperor Tenchi who transferred the capital to Omi no miya had originally designated his younger maternal half-brother Prince Oama as Crown Prince (according to the Nihonshoki [Chronicles of Japan], the younger brother of an Emperor. And also there is a theory that the story of Prince Oama was designated as heir was itself a fiction in the Nihonshoki) but on November 26, 671, he designated his own son Prince Otomo as Daijo-daijin (Grand minister of state) beginning to show his will to let Prince Otomo succeed to the throne. After that, Emperor Tenchi got sick. Prince Oama recommended Prince Otomo as Crown Prince and he told Emperor Tenchi that he wanted to be a monk and went to Yoshino no miya (Yoshino, Nara Prefecture). Emperor Tenchi accepted Prince Oama's offer.
On January 10 672, Emperor Tenchi died at the age of 46 in Omi no miya. Prince Otomo succeeded to the throne but he was only 24 years old. On July 27 672, Prince Oama departed Yoshino and escaped to Mino via Iga Province and Ise Province. In Mino, under the direction of Prince Oama, O no Honji already took up arms and Fuwa road was blocked. For this, Prince Oama was able to gather troops from various countries on Tokaido Road, Tosando Road. Entered Mino and gathered troops from the east country, and Prince Oama divided the troops in two and dispatched them in two directions; Yamato and Omi on August 3.
The Prince Otomo side in the Omi Court dispatched a messenger to Togoku (eastern country), Kibi Province, Tsukushi Province (Kyushu) to gather troops, the messenger of the east country was hampered by the troops of the Prince Oama side and they could not persuade syndics of Kibi and Tsukushi to cooperate with Prince Otomo. Even so, they could gather troops from near countries.
In Yamato, after Prince Oama left, the Omi Court gathered troops in Wakyo (old city of Asuka) but OTOMO no Fukei took up arms and gained control of the army. Fukei troops waged a fierce battle with the Omi Court army and attacked from the west and north. The Omi Court army was superior this time so the Fukei troops were often routed but Fukei regrouped the army repeatedly and beat off the enemy. In time, rescue forces led by KI no Ahemaro arrived from Mino and saved the Fukei troops from the bad situation.
The Omi Court army headed for Mino but the advancement was stopped due to bad leadership. Prince Oama's army led by MURAKUNI no Oyori moved forward and opened war at Okinaga no Yokokawa on August 8 and after that, marched into enemies with a series of victories. When the Omi Court army was badly defeated at the Battle of Seta Bridge (Karahashi-cho, Otsu City, Siga Prefecture) on August 23, Prince Otomo killed himself on August 24 the next day and the battle converged. The following year, in February 673, Prince Oama ascended to the throne and established Asuka no Kiyohara no miya.
Also a new system was established for rewards and re-establishment of order; revision of dress code system, established Yakusa no Kabane (the eight honorary titles), revision of Kan-i system (office and rank system). Emperor Tenmu proceeded with the centralized system more than Emperor Tenchi did.
The Cause of the War
There are several theories of the cause of the Jinshin War.
Before his accession, Emperor Tenchi took up arms against Siila and Tang allied forces to attempt the recovery of Baekje in 663 but this war turned into a fiasco due to the loss of the Battle of Hakusukinoe. Because of this, Emperor Tenchi made them build national defenses along the coast of the sea of Genkai, Seto Inland Sea and let refugees of Baekje immigrate to Togoku and moved the palace from Asuka in the Nara Basin to Omi no miya which is located on the southern edge of Lake Biwa. Moreover, political reform within country was radically promoted. However, it is thought that this movement became a burden for the local ruling families and citizens and produced a sense of dissatisfaction. Fire disaster occurred frequently when Omi no miya was relocated and it is said that the fires reflected the dissatisfaction of the local ruling families and citizens. Furthermore, in the reform by Emperor Tenchi, it is thought that complaints were growing between the local ruling families (especially Togoku) because they were disregarded. These growing complaints became the background of the Jinshin War.
Also, there is a theory that the war was one of the imperial succession disputes that occurred frequently in the Asuka period. At that time, Emperor Tenchi who was trying to implement the ritsuryo system (a system of centralized government based on the ritsuryo code) also trying to introduce legitimate child succession (that is, Prince Otomo [Emperor Kobun] would inherit the imperial throne) instead of the old conventional succession between brothers-uterine so Prince Oama's dissatisfaction escalated for this. Moreover, Prince Oama seemed like an efficient politician, and Prince Oama supporters who thought he should succeed the imperial throne made efforts and this led to the War. Based on these, dissatisfaction toward reform previously mentioned created the base of the Jinshin War and there is a leading theory that the cause of the Jinshin War was the dispute regarding the succession to the Imperial throne since Emperor Tenchi's era.
Also, there is a theory that the reason for this war was the friction between Emperor Tenchi and Prince Oama. Nobutomo BAN who lived in the Edo period presumed that the remote cause of the dissatisfaction between Emperor Tenchi and Emperor Tenmu was a dispute over Nukata no Okimi (woman) as in the contents of waka (Japanese poetry) written by Nukata no Okimi in the "Manyoshu" (anthology of Japanese poems).
Heresy, Common Saying
There is a thesis that the cause of the war was an internal conflict within the Kyushu dynasty (refer to the Kyushu dynasty thesis for detail).
Also there is a thesis that after the war, Prince Otomo went down to Kazusa Province through Tokaido Road (refer to Itabu station for more detail).
In China, there is a thesis that the Jinshin War was the battle of 'Wakoku' and 'Japan' (refer to the Jiu Tang Shu [Old Tang History] for more detail).