The little-understood state of Jin in the southern part of the Korean peninsula has given rise to the loose confederacies Jinhan, Byeonhan, and Mahan, or collectively, Samhan.

Jinhan, like the other Samhan confederacies, had arisen out of the confusion and migration following the fall of Gojoseon in 108 BCE.

The city-states of central and southern Korea during the so-called Proto–Three Kingdoms period had been grouped into three confederacies called Samhan.

Silla began as Saro-guk, a statelet within the twelve-member confederacy called Jinhan.

Saro-guk consists of six villages and six clans.

According to Korean records, Silla was founded by King Park Hyeokgeose in 57 BCE, around present-day Gyeongju.

Hyeokgeose is said to have been hatched from an egg laid from a white horse, and when he turned thirteen, six clans submitted to him as king and established Saro (or Seona).

He is also the progenitor of the Park clan, now one of the most common family names in Korea.

The earliest recording of this date is found in the Samguk Sagi, a twelfth-century Korean history.

Current archaeological evidence indicates that while a polity may have been established even earlier than this in the Gyeongju region, it is too early to call it a kingdom.

The author of the Samguk Sagi, Kim Bu-sik, probably attempted to legitimize Silla rule by giving it historical seniority over its rival kingdoms Baekje and Goguryeo.

According to South Korean historiography, however, it is the glories of a third kingdom that are most important in founding the nation.

Silla eventually becomes the repository of a rich and cultured ruling elite, with its capital at Kyongju in the southeast, north of the modern port of Pusan.

The military men who will rule South Korea, either as dictators or elected leaders beginning in 1961, will all come from this region, and most South Korean historians will consider Silla's historical lineage as predominant.

It is the Baekje legacy that will suffer in divided Korea, as Koreans of other regions and historians in both North Korea and South Korea discriminate against the people of the Cholla provinces in the southwest of the peninsula, but taken together, the Three Kingdoms will continue to influence Korean history and political culture.

Koreans will often assume that regional traits that they like or dislike have their origins in the Three Kingdoms period.

King Naemul (356–402) of the Kim clan establishes a hereditary monarchy in Silla, eliminating the rotating power-sharing scheme.

The leader's title, now truly royal, becomes Maripgan (from the native Korean root Han or Gan, "leader" or "great", which was previously used for ruling princes in southern Korea, and which may have some relationship with the Mongol/Turkic title Khan).

Naemul's later reign is troubled by recurrent invasions by Wa (Japan) and the northern Malgal (Mohe) tribes, sometimes considered the ancestors of the Jurchens, modern-day Manchus and other Tungusic peoples.

This begins with a massive Japanese incursion in 364, which is repulsed with great loss of life.

King Naemul of Silla is the first king to appear by name in Chinese records.

It appears that there was a great influx of Chinese culture into Silla in his period, and that the widespread use of Chinese characters begins in his time.

In 381, Silla sends emissaries to China and establishes relations with Goguryeo.

Silla submits to Goguryeo in 399 for protection from raids from Baekjae.

Many consider this loose unification under Goguryeo to have been the first and only true unification of the Three Kingdoms.

Silla, another Korean kingdom in the southeast of the peninsula, requests the assistance of Goguryeo in 400 to defend against an alliance of a Japanese army, the Baekje kingdom to the west, and the Gaya Confederacy to the southwest.

In the same year, King Gwanggaeto responds with fifty thousand troops, defeats both Japanese and Gaya cavalry units, and makes both Silla and Gaya submit to his authority.

Silla, one of the Three Kingdoms of Korea, formally adopts Buddhism as a state religion in approximately 527.

Silla conquers the city-state of Geumgwan Gaya during Korea’s Three Kingdoms Period.

After Geumgwan Gaya capitulates to Silla in 532, its royal house is accepted into the Sillan aristocracy (probably because by this time, a major noble house of Silla, the Gyeongju Kim clan, is related to the Gaya royal house, which is the Gimhae Kim clan) and given the rank of "true bone," the second-highest level of the Silla bone rank system.

The late seventh century General Kim Yu-shin of Silla, a member of the Gimhae Kim clan, is a descendant of the last king of Gaya.

Baekje and the Gaya Confederacy wage war upon Silla, one of the Three Kingdoms of Korea, but are defeated.