The Old Book of Tang (旧唐書)

"The Old Book of Tang" (Jiu Tangshu or Kutojo in Japanese) was a book of history compiled by Liu Xu and others under the reign of Shi Chonggui of Later Jin of the Five Dynasties and Ten Kingdoms Period in China. It is counted among the Twenty-Four Dynastic Histories. It recounts the rise and fall of the Tang Dynasty (618 -907). It was originally called "The Book of Tang" which was changed to "The Old Book of Tang" when "The New Book of Tang" was compiled.

It was completed in 945, and the following year the Later Jin Dynasty came to an end. The editor in chief changed while it was still being compiled, resulting in many editorial problems: two chapters for a single figure; disproportionately richer information on the earlier Tang and fewer accounts on the later Tang. This made it unpopular in later times, and it was revised into "The New Book of Tang" in the Northern Sung period. However, it is regarded as more valuable than "The New Book of Tang" as it contains the literal transcriptions of raw materials.

It seems that the editorial processes played a part in providing two chapters on Japan: "The Book of Wakoku" and "The Book of Nipponkoku" in the Old Book of Tang. This tradition of two Japans was continued into "Taiping Yulan" (The Imperial Readings of the Taiping Era) compiled under the early Sung (Dynasty).
The section on Wakoku (Nippon) is interrupted by the descriptions of the Battle of Hakusukinoe and the Jinshin War, which are inserted between 'The Book of Wakoku' and 'The Book of Nipponkoku.'
Osamu OBA argued that this was not a simple editorial mistake. Rather, some Chinese in that period held the view that 'Wakoku (Emperor Tenchi)' was defeated at the Jinshin War and 'Nipponkoku (Emperor Tenmu)' was established. Oba suggested that the editors who did not come to a definite conclusion may have given two accounts of Japan.
However, 'The Section on Eastern Barbarians' mentions as follows:
Nipponkoku is different from Wakoku.'
The country is near the sun and is hence called Nippon.'
Some say that the people do not find the name of Wakoku beautiful and changed it to Nippon.'
Others say that Nippon was a small country so that it integrated Wakoku.'
Thus, such a more generally accepted view is also narrated in the text.

The text consists of 200 volumes: 20 volumes of 'Benji' (Imperial Biographies), 150 volumes of 'Liezhuan' (Biographies of Important Individuals) and 30 volumes of 'Shi' (various genres). It is narrated in a style of biographical history.