[1] The three kingdoms occupied the entire peninsula and roughly half of Manchuria (modern-day Northeast China and small parts of the Russian Far East).

[5][6] The period ended in the 7th century, after Silla allied with Tang China and unified the peninsula for the first time in history.

After the fall of Baekje and Goguryeo, the Tang dynasty established a short-lived military government to administer parts of the Korean Peninsula.

[8] In a letter to an imperial tutor of the Tang dynasty, Ch'oe Ch'i-wŏn equated Byeonhan to Baekje, Jinhan to Silla, and Mahan to Goguryeo.

[8] In his Ten Mandates to his descendants, Wang Geon declared that he had unified the Three Han (Samhan), referring to the Three Kingdoms of Korea.

[11] For example, the epitaph of Go Hyeon (고현; 高玄), a Tang dynasty general of Goguryeo origin who died in 690, calls him a "Liaodong Samhan man" (요동 삼한인; 遼東 三韓人; Yodong Samhanin).

The Three Kingdoms were founded after the fall of Wiman Joseon and gradually conquered and absorbed various other small states and confederacies.

After the fall of Gojoseon, the Han dynasty established four commanderies in the northwestern Korean Peninsula[12][13][14][15][16] and present Liaoning.

The nascent precursors of Baekje and Silla expanded within the web of statelets during the Proto-Three Kingdoms period, and Goguryeo conquered neighboring state like Buyeo in Manchuria and chiefdoms in Okjeo, Dongye which occupied the northeastern Korean Peninsula.

The Book of Sui (Volume 81) recorded: "The customs, laws and clothes of Goguryeo, Baekje and Silla are generally identical.

[20] "The decline of Chinese power in the fourth century unleashed a wave of refugees that proved pivotal in speeding up the process of state-building in Korea," starting the Three Kingdoms era.

[21] Goguryeo emerged on the north and south banks of the Yalu (Amrok) River, in the wake of Gojoseon's fall.

At the beginning, the state was located on the border with China; it gradually expanded into Manchuria and destroyed the Chinese Lelang commandery in 313.

Two sons of the founder of Goguryeo are recorded to have fled a succession conflict, to establish Baekje around the present Seoul area.

[31][32][33] Baekje absorbed or conquered other Mahan chiefdoms and, at its peak in the 4th century, controlled most of the western Korean Peninsula.

Baekje was once a great military power on the Korean Peninsula, especially during the time of Geunchogo,[39] but was critically defeated by Gwanggaeto and declined.

According to Korean records, in 57 BC, Seorabeol (or Saro, later Silla) in the southeast of the peninsula unified and expanded the confederation of city-states known as Jinhan.

[41][42] Renamed from Saro to Silla in 503, the kingdom annexed the Gaya confederacy (which in turn had absorbed Byeonhan earlier) in the first half of the 6th century.

Archaeologists use theoretical guidelines derived from anthropology, ethnology, analogy, and ethnohistory to the concept of what defines a state-level society.

In anthropological archaeology the presence of urban centres (especially capitals), monumental architecture, craft specialization and standardization of production, ostentatious burials, writing or recording systems, bureaucracy, demonstrated political control of geographical areas that are usually larger in area than a single river valley, etc.

Rhee and Choi hypothesize that a mix of internal developments and external factors lead to the emergence of state-level societies in Korea.

These sites are part of what was an interconnected and sprawling ancient industrial complex on the northeast outskirts of the Silla capital.

Songok-dong and Mulcheon-ri are examples of the large-scale of specialized factory-style productions in the Three Kingdoms and Unified Silla periods.