Wakoku

Wakoku (倭國) was the name used by early imperial China and its neighbouring states to refer to the nation usually identified as Japan. There are various theories regarding the extent of power of the early kings of Japan. According to the Book of Sui and the History of the Northern Dynasties, its borders were five months from east to west and three months from north to south. The Wajin appear in historical documents such as the Book of Han and the Geographical Survey of Japan from around the 2nd century BC. In the late 7th century, the Yamato kingdom, which had been called Yamato, changed its external name to Japan, but its relation to Japan since Book of the Later Han is not clear. There are discrepancies in the descriptions of the Old Book of Tang and the New Book of Tang.