Isshi Incident (乙巳の変)

The Isshi Incident was a coup which occurred during Asuka period when Emperor Tenchi and FUJIWARA no Kamatari assassinated SOGA no Iruka inside the Imperial Court, which led to the fall of the Soga clan (head family of the Soga clan). After that, Prince Naka no Oe carried out a reform called the Taika Reforms. Although the assassination of SOGA no Iruka is sometimes referred to as the 'Taika Reforms,' the series of political reforms carried out after the 'Isshi Incident,' which was a coup d'etat, are the 'Taika Reforms' in a narrow sense.

Details behind the incident
The following is the summary of the incident recorded in 'Nihonshoki' (Chronicles of Japan).

Tyranny of the Soga clan
Prince Umayado (also known as Prince Shotoku) who was in charge of the Imperial Court died on April 11, 622. Due to the death of Prince Shotoku, there was no one who could control such powerful family as Soga clan, and thus the Soga clan began exercising tyrannical power that eventually exceeded the power of the Imperial Family.

On June 22, 626, SOGA no Emishi became a minister after the death of his father, SOGA no Umako. On April 18, 628, Empress Suiko passed away without deciding her successor. Emperor Jomei and Prince Yamashiro no Oe (a son of Prince Shotoku) claimed the right of succession to the Imperial Throne. Prince Yamashiro no Oe had a closer blood relation with the Soga clan (Prince Shotoku was biologically related to the Soga clan, and Prince Yamashiro no Oe's mother was a younger sister of Emishi), however, Emishi recommended Prince Tamura for the next Imperial Throne since he disliked Jogu Oke (Prince Shotoku's family line) to gain more power by choosing the competent prince Yamashiro no Oe for the next emperor. Emishi enthroned Prince Tamura by murdering his uncle SAKAIBE no Marise who recommended Prince Yamashiro no Oe. He became Emperor Jomei. Since the Soga clan gained even more power, members of powerful clans stopped attending to the Imperial Court, but instead regularly visited the residence of the Soga family to serve them. Although Prince Oha (a son of Emperor Bindatsu) made a suggestion of ringing a bell as a sign for the officials to come out to serve the Imperial Court since they were neglecting their duties, this idea was refused by Emishi.

On November 20, 641, Princess Takara was enthroned after the death of her husband, Emperor Jomei. She became Empress Kogyoku. The tyranny of the Soga clan became more excessive. In July, 642, when Emishi offered a statue of Bosatsu as well as Shitenno (the Four Devas) statues to Hyakusai-ji Temple and gathered a group of monks to read a sutra and burn incense to pray for rain due to a long drought, it rained a little bit the next day but did not the following day. In August, as soon as Empress Kogyoku prayed for rain by bowing to all directions along the river in Minamibuchi, thunder started rumbling and it kept raining for five days. People called her 'Shitoku Emperor' (meaning the most competent emperor). It explained what was written later in 'Nihonshoki' by stating that the Soga clan and the Imperial Family compared the ability as a prayer which was seen as one of the qualifications for the leader in ancient Japan and that the Imperial Family was more competent.

In the same year, Emishi and his son Iruka mobilized citizens including members of Prince Shotoku's family to construct their mausoleum, which made a daughter of Prince Shotoku, Princess Iratsume, very angry.

In October, 643, due to his sickness, Emishi handed over his rank Shikan to Iruka which allowed him to be a minister and let his second son to be Mononobe minister without the permission from the Imperial Court.
(It was because their grandmother was a sister of MONONOBE no Moriya.)

Fall of Jogu Oke
In November of the same year, Iruka felt the need to kill Prince Yamashiro no Oe who had the right of succession to the Imperial Throne since he wanted Prince Furuhito no Oe to be the next emperor who was biologically related to the Soga clan. Iruka sent troops led by KOSE no Tokuta and HAJI no Saba no Muraji to attack Ikaruganomiya Palace where Prince Yamashiro no Oe resided. Prince Yamashiro no Oe and dozens of his palace servants fought back madly and killed HAJI no Saba no Muraji, however, they were forced to evacuate to Mt. Ikoma. When Prince Yamashiro no Oe's close adviser, MIWA no Fumiya no Kimi, suggested him to escape to the east, he turned down this offer by saying he did not want the citizens to suffer anymore. After returning to Ikaruga-dera Temple, Prince Yamashiro no Oe committed suicide with his children which led to the fall of Jogu Oke by leaving no descendants of Prince Shotoku.
When Emishi heard about Iruka's outrage against Prince Yamashiro no Oe and his family, he responded by saying 'you put yourself in danger.'

Assassination of SOGA no Iruka
Since NAKATOMI no Kamako whose clan was in charge of important national rites detested the tyranny of the Soga clan, he secretly worked out a plan to overthrow the clan. Kamako first approached Emperor Kotoku, however, he needed someone who was more capable of playing the central role in the coup.

Kamako picked up Prince Naka no Oe's shoe when it came off and presented it to him when they were playing a ball game at Horyu-ji Temple. It brought them close together. It is said that Prince Naka no Oe and Kamako held a secret conversation about the overturn of the Soga clan on their way home and to the MINABUCHI no Shoan's private school where they learned the teachings of Shuko and Confucius. Kamako also convinced SOGANOKURA-YAMADA no Ishikawamaro who was a dominant figure in the Soga clan to be their comrade, and his daughter married to Prince Naka no Oe.

In 645, messengers from Three Kingdoms of Korea (Silla, Baekje and Goguryeo) came to Japan to deliver some gifts (called Sangoku no Shirabe). This ceremony of Sangoku no Shirabe was going to be held in the Imperial Court, and Iruka would definitely attend as a minister. Prince Naka no Oe and Kamako saw this occasion as the perfect timing to carry out the assassination plan.
(According to Daishokukanden [a book written by FUJIWARA no Nakamaro in the eighth century] the visit of envoys from Three Kingdoms of Korea to Japan was a setup to lure Iruka.)

On June 12 of the same year, when Empress Kogyoku arrived at Daigokuden having Prince Furuhito no Oe guarding her close by, Iruka entered the Imperial Court where the ceremony of Sangoku no Shirabe took place. Although Iruka was a very cautious man and always carried his sword day and night, they prepared an actor to convince him to take his sword off. Prince Naka no Oe ordered gate guards to close the palace gates. The Johyobun (memorial to the Emperor) were read by ISHIKAWA no Maro. Prince Naka no Oe hid on the palace side with holding a long spear while Kamako lurked with a bow and arrow. They made AMANOINUKAI no Katsumaro carry two swords and let SAEKI no Komaro and KATSURAGINO-WAKAINUKAINO Amita have each.

Those two who were given the role to actually kill Iruka were so terrified that they threw up immediately after eating rice mixed with water. Kamako reprimanded them. As ISHIKAWA no Maro carried on reading the memorials, he began sweating and his voice and hands started shaking since Komaro did not show up.
Iruka found it suspicious and asked 'why are you shaking?'
ISHIKAWA no Maro answered by saying 'I am sweating because it is such an honor to be close to the empress.'

Prince Naka no Oe jumped out thinking Komaro was too frightened of Iruka to carry out the plan. Komaro and others jumped out as well and slashed Iruka's shoulder and head. When Iruka stood up surprised, Komaro cut one of his legs.
Iruka fell over and said to the empress by prostrating himself 'What did I do to deserve this treatment? Please punish them.'
The empress was very shocked and asked Prince Naka no Oe why.
Prince Naka no Oe answered by saying 'Iruka tried to usurp the Imperial Throne by killing members of the Imperial Family.'
Empress Kogyoku immediately left to the inside of the palace. Komaro and WAKAINUKAINO Amita completed the killing of Iruka. It rained heavily that day, and therefore, the garden was flooded with water. Iruka's body was thrown out to the garden and covered with a shoji screen (a paper sliding door).

Fall of the head family of the Soga clan and the Taika Reforms
Prince Furuhito no Oe ran back to his place (it is suggested that he then said 'Koreans killed Iruka'). Prince Naka no Oe immediately returned to Asuka-dera Temple and prepared for war. Other princes and powerful families followed his action. Although naturalized citizens of the Yamatonoaya clan gathered at the Soga clan's house to support Emishi, KOSE no Tokuta who was sent by Prince Naka no Oe managed to convince them to leave, which made troops on the Soga side scattered away (another theory states that the Soga clan lost their will to fight when Prince Furuhito no Oe became a monk at Asuka-dera Temple since he was who they were fighting for).

The next day, on June 13, Iruka set his house on fire to commit suicide, burning down rare items like "Tennoki" (Record of the Emperors) and "Kokki" (National Record). FUNE no Fuhito Esaka was able to save "Kokki" from the fire and presented it to Prince Naka no Oe. This was how the tyranny exercised by the head family of the Soga clan over the years was ended.

On June 14, Empress Kogyoku abdicated the throne and handed over the position to Prince Karu. He became Emperor Kotoku. Prince Naka no Oe became the crown prince. Prince Naka no Oe appointed ABE no Uchimaro as Sadaijin (Minister of the Left) and SOGANOKURA-YAMADA no Ishikawamaro as Udaijin (Minister of the Right). NAKATOMI no Kamako was appointed as Uchi no Omi (an important governmental post presiding over important state affairs while assisting the Emperor) and later carried out a reform called the Taika Reforms.

Various theories
The theory of Prince Karu being the ringleader
The theory states that from the circumstance evidence Prince Karu was the true ringleader and killed the Soga clan in order to carry out the Japanese first abdication; Kogyoku stepping down from the throne and Kotoku ascending the throne (suggested by Mitsuo TOYAMA).

Peninsular model theory
Takashi YOSHIDA's view states that the reason SOGA no Iruka strove for the concentration of authority by destroying Prince Yamashiro no Oe was to do with the coup carried out by Gaisobun EN in Goguryeo, and furthermore; Isshi Incident was easily accepted by the officials since it was similar to the enthronement of the Queen under the Royal Family based on the political structure formed after the suppression of Pidam War done by Yushin KIM in Silla.

Reactionary coup theory
According to the results of the excavation which started from 2005, the SOGA no Iruka's residence was found on Amakashi Hill in Asuka as well as the barracks and weapon storage at 'Tani no Mikado.'
Furthermore, another theory states that judging from the locations of SOGA no Emishi residence and Asuka-dera Temple, the Soga clan was trying to guard the capital by building forts around Asuka Itabuki no Miya Palace.

The Soga clan had a sense of danger that Japan was also exposed to the menace of Tang Dynasty which was founded in 618 as it was growing its clout in the Korean peninsula. Therefore, they considered shifting the policy which was focused on Baekje to another that would build cooperative diplomatic relations with each country.
On the other hand, the conservatives like NAKATOMI no Kamako and Prince Naka no Oe were in favor of their original 'Baekje focused' policy, and therefore destroyed the Soga clan who were 'liberals.'
After the fall of the Soga clan, the conservatives moved ahead with the Baekje focused policy, which failed when the Battle of Hakusukinoe (the battle of Baekgan) broke out. It is thought that the so called 'Taika Reforms' were carried out after that.