North–South States Period

Later Silla

After the unification wars, the Tang Dynasty established territories in the former Goguryeo, and began to administer and establish communities in Baekje. Silla attacked the Chinese in Baekje and northern Korea in 671.

The Tang Dynasty then invaded Silla in 674 but Silla defeated the Tang army in the north. Silla drove the Tang forces out of the peninsula by 676 to achieve unification of most of the Three Kingdoms.

Later Silla was a golden age of art and culture, and Buddhism became a large part of Silla culture. Buddhist monasteries such as the Bulguksa are examples of advanced Korean architecture and Buddhist influence. State-sponsored art and architecture from this period include Hwangnyongsa Temple, Bunhwangsa Temple, and Seokguram Grotto, a World Heritage Site.

Later Silla carried on the maritime prowess of Baekje, which acted like the Phoenicia of medieval East Asia, and during the 8th and 9th centuries dominated the seas of East Asia and the trade between China, Korea and Japan, most notably during the time of Jang Bogo; in addition, Silla people made overseas communities in China on the Shandong Peninsula and the mouth of the Yangtze River. Later Silla was a prosperous and wealthy country, and its metropolitan capital of Gyeongju was the fourth largest city in the world.

Buddhism flourished during this time, and many Korean Buddhists gained great fame among Chinese Buddhists and contributed to Chinese Buddhism, including: Woncheuk, Wonhyo, Uisang, Musang, and Kim Gyo-gak, a Silla prince whose influence made Mount Jiuhua one of the Four Sacred Mountains of Chinese Buddhism.

Silla began to experience political troubles in the late 9th century. This severely weakened Silla and soon thereafter, descendants of the former Baekje established Later Baekje. In the north, rebels revived Goguryeo, beginning the Later Three Kingdoms period.

Later Silla lasted for 267 years until, under King Gyeongsun, it was annexed by Goryeo in 935.

Balhae

Balhae, the name of which was another transcribed version of Mohe (靺鞨, a Tungus Tribe speaking a language like Manchurian and Sibe), was founded after Goguryeo had fallen. It was founded in the northern part of former lands of Goguryeo by Dae Joyeong, a former Goguryeo general, after defeating the military of central government of Tang Dynasty at the Battle of Tianmenling. Balhae controlled the northern areas of the Korean Peninsula, much of Manchuria, and expanded into present-day Russian Maritime Province. Balhae styled itself as Goguryeo's successor state.

In a time of relative peace and stability in the region, Balhae flourished in culture, especially during the long reign of the third King Mun (r. 737-793) and King Seon. At that time, Balhae was a culturally advanced country, so that even China referred to this kingdom as "a prosperous country of the East." However, Balhae was severely weakened by the 10th century, and the Khitan Liao Dynasty conquered Balhae in 926.

Goryeo absorbed some of Balhae's territory and received Balhae refugees, including the crown prince and the royal family, but compiled no known histories of Balhae. The 18th century Joseon dynasty historian Yu Deukgong advocated the proper study of Balhae as part of Korean history, and coined the term "North and South States Period" to refer to this era.

Language

Due to the lack of linguistic evidence, it is difficult to make a definitive conclusion for the linguistic relation between the Balhae and Silla languages.

Shoku Nihongi implies that the Balhae language, a Goguryeo language, and Silla language share a close relationship: a student sent from Silla to Japan for an interpreter training in Japanese language assisted a diplomatic envoy from Balhae in communicating during the Japanese court audience.

Because of the official and wide use of Chinese written system, there are only two surviving Balhae words: kundufu (transcribed as 可毒夫) meaning "king" and furuki for "stable". They seem to have more Tungusic linguistic relationship and origins than Koreanic.