The   were kings of ancient Japan who sent envoys to China during the 5th century to strengthen the legitimacy of their claims to power by gaining the recognition of a Chinese emperor during the chaotic period of the Northern and Southern dynasties, when either dynasty was desperate to gain legitimacy over the other by trying to assert itself as the granter of official titles, through garnering as many foreign countries willing to receive titles.

Details about the five kings are unknown. According to written records in China, their names were San (), Chin (), Sai (), Kō () and Bu (). But no kings with such names appear in the Japanese records, and where during this time only 3 appear instead of 5, spurring much debate of their identities.

Titles for the Kings of Wa 
In summary, the monarchs of Wa repeatedly asked for the titles:

  (King of Wa Country)
 使持節 (Highest Rank Military Commander)
  (Grand Peacekeeper-General of the East)
 都督-region-諸軍事 (Commander of All Military Affairs of listed regions)

The Southern dynasty of Liu Song (not to be confused with the Song), with the most interaction with the 5 Kings of Wa, readily granted the title of King of Wa on request, but repeatedly refused them the 二品 Class 2, 6th rank  (Grand Peacekeeper-General of the East), and bestowed them the 三品 Class 3, 3rd rank  (Peacekeeper-General of the East) instead until their final year of reign when their waning power rendered them desperate for allies.

Peacekeeper-General of the East 
In the Liu Song, the highest rank of military commanders were all in Class 2 of the Nine-Rank System based off of the system used in the Jin Dynasty (Liang Dynasty and Chen Dynasty used the 武職二十四班 24-Class Martial Occupation system instead). These were also bestowed to the rulers of the subject state (located in the East of China) who sent envoy to the emperor of the Dynasty. The highest general title was  (Grand General conquering the East). The next highest title was  (Grand Suppressor-General of the East). The third highest and the lowest among three was  (Grand Peacekeeper-General of the East).

In the Song dynasty, the emperors bestowed 3 eastern monarchies (夷):

 413 -  (Grand Conqueror-General of the East) to the King of Goguryeo. Class 2, 4th rank.
 463 - promoted 2 ranks to 車騎大將軍 (Grand Chariot-General). Class 2, 2nd rank.
 416 -  (Suppressor-General of the East) to the King of Baekje. Class 3, 2nd rank.
 420 - promoted to  (Grand Suppressor-General of the East). Class 2, 5th rank.
 421 -  (Peacekeeper-General of the East) to the King of Wa. Class 3, 3rd rank.
 478 - promoted to  (Grand Peacekeeper-General of the East) to the King of Wa on the last year of the Liu Song dynasty. Class 2, 6th rank.

It should be noted, of these 3 eastern countries, only the Wa were recorded to have visited Song already with 自稱 (self-proclaimed) titles.

There are interpretations on this fact that the King of Goguryeo stood in the highest rank, and the King of Wa stood in the lowest rank, while the King of Baekje stood between Goguryeo and Wa. But there are also other opinions against this interpretation. The difference of general ranks among the three states (Goguryeo, Baekje, and Wa) was due to the order which each state had first sent envoy to the dynasty, and it cannot be said that the ranks of Goguryeo and Baekje were substantially higher than that of Wa. Sakamoto also points out the different view on these general titles.

But these assertions are refutable; seeing that the Class 2  title is a specific self-proclaimed title by the Wa, not one where the Wa asked to be have any available Class 2 generalship and the Liu Song deciding to relegate them behind Baekje without Wa's consent. Furthermore, If the Wa in asking for affirmation in their self-proclaimed  title were deliberately humbling themselves to be ranked behind the Goguryeo and Baekje in the Liu Song hierarchy, then Baekje would not be included in Sai's 438 self-proclaimed Command of All Military Affairs of Six Countries, nor would it be included in Bu's 477 self-proclaimed Command of All Military Affairs of Seven Countries.

Wang Jiànqún 王健群, points out that the fact Wa's frequent askance for recognition, undermines credence to their claim, on top of their self-proclaimed titles being rejected and given a lower grade title

Song is destroyed in 479, and with a shift in Chinese dynasties, a new titles were issued anew:

 479 - Without any envoys sent there, the newfound Qi dynasty voluntarily gives out titles as a celebratory gesture and establishing itself as a granter of coveted titles. Qi bestows in 479:
 Class 2, 1st rank  (Grand Fast-Cavalry General) to the King of Goguryeo, automatically promoted 1 rank from Song's 開府儀同三司 and Class 2, 2nd rank 車騎大將軍 (Grand Chariot-General), titles for the King of Goguryeo.
 Class 2, 5th Rank  (Grand Suppressor-General of the East) to the King of Wa, from Class 2, 6th rank . 
 The King of Baekje would receive the same  title upon sending an envoy in 495.
 Class 3, 14th rank  (Assisting General) to the Haji of Gaya, but not automatically, it sent an envoy in 479.
 502 - Without any envoys sent there, the newfound Liang dynasty voluntarily gives out titles as a celebratory gesture and establishing itself as a granter of coveted titles. The Liang first used 24-Class (班) system where the higher number denoted higher rank, until later adding up to 34 classes. Liang bestows in 502:
 車騎大將軍 (Grand Chariot-General) to Munjamyeong of Goguryeo, from 車騎將軍 (Chariot-General). Promotion from 24th Class, 6th rank to 3rd rank.
 征東大將軍 (Grand Conqueror-General of the East) to Dongseong of Baekje, from  (Grand Suppressor-General of the East). Promotion from 23rd Class, 3rd rank to 24th Class, 7th rank.
 征東大將軍 (Grand Conqueror-General of the East) to Bu of Wa, from  (Grand Suppressor-General of the East). Promotion from 23rd Class, 3rd rank to 24th Class, 7th rank.
 鎮西將軍 (Suppressor-General of the West) to King Liangmi He of DangChang, from 安西將軍 (Peacekeeper-General of the West) Promotion from 21st Class, 3rd rank to 22nd Class, 3rd rank.
 征西將軍 (Conqueror-General of the West) to King Xiuliudai of Tuyuhun from 鎮西將軍 (Suppressor-General of the West). Promotion from 23rd Class, 3rd rank to 22nd Class, 3rd rank.

Regional Appointments 
Comparing contemporary historical records of the regions in the Korean peninsula around this time, and numerous discrepancies listed below, it is obvious these claims are false. In context, exploiting China's lack of interest in eastern matters to lay false claim over neighboring territories was not a new custom in East Asia. Baekje itself had claimed that Silla is under its control prior; Goguryeo claimed Baekje and Silla are both under its control.

 438 - Chin petitions official appointment of the self-proclaimed title, Commander of All Military Affairs of: 倭百濟新羅任那秦韓慕韓六國
 6 Countries of Wa - Baekje - Silla - Imna - Jinhan - Mohan (Mahan)
 Of note are Jinhan and Mohan, countries that have already ceased to exist centuries ago. This already undermines his claim in both that they do not exist, or would be redundant locales as they are now part of other countries:
 Countries of the Jinhan Confederacy were one by one annexed into Silla around 1st to 3rd century.
 Countries of the Mohan (Mahan) Confederacy were one by one annexed into Baekje by the 4th century.
 451 - Liu Song entitles Sai to Commander of All Military Affairs of: 倭新羅任那加羅秦韓慕韓六國
 6 Countries of Wa - Silla - Imna - Gaya - Jinhan - Mohan (Mahan)
 Liu Song did not approve of the Wa laying claim to Baekje and removed it from their entitlement. This is because Jeonji of Baekje already contacted Liu Song and was recognized as  (Suppressor-General of the East) in 416, and  (Grand Suppressor-General of the East) in 420. The other countries were not in contact with Song.
 Instead, without Sai requesting it, Liu Song appointed Sai to the Gaya Confederacy, which was interchangeable with the region of Imna. This sloppy redundancy is an important evidence that shows Liu Song's own half-hearted attitude.
 477 - Bu petitions official appointment of self-proclaimed title, Commander of All Military Affairs of: 倭百濟新羅任那加羅秦韓慕韓七國
 7 Countries of Wa - Baekje - Silla - Imna - Gaya - Jinhan - Mohan (Mahan)
 Of note is Bu going along with Liu Song's sloppy mistake of adding in Gaya, showing he too knows as little as the Liu Song of the lands he claims to rule over, undermining the claim's credence even further.
 Bu requests reaffirmation of being appointed to what Sai was appointed to, in addition to reattempting to be appointed to Baekje.
 478 - Liu Song entitles Bu to Commander of All Military Affairs of: 倭新羅任那加羅秦韓慕韓六國
 6 Countries of Wa - Silla - Imna - Gaya - Jinhan - Mohan (Mahan)
 Liu Song once again ignores Wa's request to add in Baekje, and only reaffirms what Sai was appointed to in 451.

Also, a few entries prior to the Kings of Wa, the Book of Song in introducing the Baekje, described that Baekje rules the Liaoxi region while Goguryeo rules the Liaodong region. This blatant inaccuracy is also evidence that Liu Song was rather uninformed or uninterested in keeping accurate knowledge of geopolitical situations out east.

Chinese records

Comparison with the Nihon Shoki

As the name of kings recorded in Chinese history are very different from the names of Emperors in the Nihon Shoki, the specification of which emperor was the one recorded is the subject of numerous disputes which have endured for centuries. Most contemporary historians assign the five Japanese kings to the following emperors (two possibilities are identified for the Kings San and Chin), mostly based on the individual features of their genealogies reported in the Chinese sources.

On the other hand, archeological evidence, such as the  inscriptions on the Inariyama and Eta Funayama Sword, also supports the idea that Bu is an equivalent of Emperor Yūryaku, who was called Wakatakeru Ōkimi by his contemporaries.

San  : Emperor Nintoku or Emperor Richū
Chin : Emperor Hanzei or Emperor Nintoku
Sai  : Emperor Ingyō
Kō   : Emperor Ankō
Bu   : Emperor Yūryaku

Since Bu is most likely to be Yūryaku, Kō, who is said to be Bu's older brother, is likely to be an equivalent of Ankō, who is also noted in the Nihonshoki as an elder brother to Yūryaku. However, the Book of Song records Kō as "Crown Prince Kō"; there is a possibility that he is not Ankō, but rather Prince Kinashi no Karu, who was a crown prince of Ingyō.

See also

Kofun Period
 Wakoku

Notes

References

External links
 石井正敏 (2005年6月). (ja) “5世紀の日韓関係 - 倭の五王と高句麗・百済 -”. 日韓歴史共同研究報告書（第1期） (日韓歴史共同研究). オリジナル の2015年10月18日時点におけるアーカイブ。

Kofun period
Yamatai
Five kings of Wa