Goryeo did not compile (修) a history of Balhae and so [we] know that Goryeo was not fully vibrant (不振). In the past, the Go clan (高氏) resided in the north and [their land was] called Goguryeo; the Buyeo clan (夫餘氏) resided in the southwest and were called Baekje; and the Bak (朴), Seok (昔) and Kim (金) clans were in the southeast and called Silla. These were the Three Kingdoms. Appropriately there was a history of the Three Kingdoms which Goryeo had [duly] compiled. This was right.
Subsequently the Buyeo and Go clans came to an end; the Kim clan occupied the south whilst the Dae clan (大氏) occupied the north and [its country] was called Balhae. These were the Southern and Northern Kingdoms and there should have befittingly been a history of the Southern and Northern Kingdoms, but Goryeo did not compile one. This was wrong.
Who were the Dae clan? They were Goguryeo people. What land was it they occupied? It was Goguryeo land. They drove [others] out (斥) to the east, west and north and enlarged [the territory].
Subsequently [both] the Kim and Dae came to an end; the Wang clan (王氏) came to power (統) and, occupying [the former territories, their country] was called Goryeo. In the south they occupied all of the Kim clan’s [former] territory but in the north they could not occupy all of the Dae’s. Some of it went to the Jurchen (女眞) and some to the Khitan (契丹). At that time those who devised plans (計) for Goryeo should have quickly compiled a history of Balhae. They [should have] taken this to the Jurchen and remonstrated them saying, “Why don’t you return our Balhae territory? Balhae’s territory was Goguryeo territory!” Then [they should have] sent a military general to go and take [the territory] and that way they could have occupied to the north of the Tomun (土門 present day Tumen) [river]. Then [similarly they should have] taken [the history] to the Khitan and remonstrated them saying, “Why don’t you return our Balhae territory? Balhae’s territory was Goguryeo territory!” Then [they should have] sent a military general to go and take [the territory] and that way they could have occupied to the west of the Amnok (鴨綠 present day Yalu) [river]. [However], in the end no [such] history of Balhae was compiled and so no one knew which clan’s land they were, either to the north of the Tomun or to the west of the Amnok. [Even if] they wanted to remonstrate the Jurchen there was nothing they could say. [Even if] they wanted to remonstrate the Khitan, there was nothing they could say.
Goryeo in the end became a weak country because it was unable to reclaim (得) the Balhae territory. How lamentable! Perhaps [Goryeo people even] said, “Balhae was overthrown by the [Khitan] Liao how could its history be compiled?” This is not so. Balhae had a system of government (憲) resembling China’s and it would certainly have had a history bureau (史官). Its capital, Holhan-seong (忽汗城), was destroyed [but] those who fled to Goryeo with the crown prince [numbered] in the hundreds of thousands. [So even if] there were no official historians [amongst them] there would definitely have been books; [even] if there were no historians or books, [they could have] asked the crown prince and been able to learn the court [history] (世). They could have asked the Eun Gyejong (隱繼宗) and learnt [about Balhae’s] ritual behaviour (禮). If they asked the [remaining] hundreds of thousands, there is nothing that they could not have found out.
Zhang Jianzhang (張建章 806-866, see note below) was from Tang [China], yet he authored the Bohaiguo-ji (渤海國記 Record of Bohai/Balhae); [how is it, there were] Goryeo people but they were unable to compile a history of Balhae themselves?
Ah! It is [now] centuries after the literature [pertaining to Balhae] has been scattered and lost. Even if one attempts to compile [a history, the sources] cannot be obtained! Whilst [working] as an official at the Naegak (內閣, refers to Gyujanggak royal library) I extensively read royal/rare books (秘書 lit. ‘secret books’) and selectively compiled (撰次) the matters [concerning] Balhae as nine go short studies (考) on [the following]: rulers (君), subjects/officials (臣), geography, ranks and titles, ceremonial texts (儀章), produce (産物), language, literature and successor states. That they cannot be termed [under the orthodox categories of] important houses (世), biographies (傳) and treatises (志) but [only] go [means] this is not a complete history. [I] would not dare pretend this is an [official] history [史].
15th day, 3rd [lunar] leap month of Gabjin (甲辰 1784)
Zhang Jianzhang (張建章 806-866) served as a Tang emissary to Barhae, his tomb was discovered in Beijing in 1956. In 832 a Balhae emissary visited Youzhou (幽州, modern Beijing) and the following year Zhang was sent to Balhae. He arrived in the capital of Balhae in the 9th lunar month of 834 and returned Youzhou in the 8th month of 835. Based on this visit he authored the three volume Bohai-ji (渤海記 Record of Bohai); it has not survived but is thought to have been a primary reference for the ‘Bohai-zhuan’ (渤海傳) section of the Xin-Tangshu (新唐書 New Book of Tang). (See Song 2012:41)
Song Gi-ho 송기호 (translator). 2012: 발해고 (Study of Balhae). Seoul: (주)홍익출판사