[5] Baekje was founded by Onjo, the third son of Goguryeo's founder Jumong and Soseono, at Wiryeseong (present-day southern Seoul).

Baekje, like Goguryeo, claimed to succeed Buyeo, a state established in present-day Manchuria around the time of Gojoseon's fall.

At its peak in the 4th century, Baekje controlled most of the western Korean peninsula, as far north as Pyongyang, and may have even held territories in China, such as in Liaoxi, though this view is controversial.

[note 1] According to the Samguk sagi, Baekje was founded in 18 BCE[1] by King Onjo, who led a group of people from Goguryeo south to the Han River basin.

Realizing Yuri would become the next king, Soseono left Goguryeo, taking her two sons Biryu and Onjo south to found their own kingdoms with their people, along with ten vassals.

In shame, Biryu committed suicide, and his people moved to Wiryeseong, where King Onjo welcomed them and renamed his country Baekje ("Hundred Vassals").

King Gaeru is believed to have moved the capital north of the river to Bukhansanseong in 132, probably in present-day Goyang to the northwest of Seoul.

In 249, according to the ancient Japanese text Nihonshoki, Baekje's expansion reached the Gaya confederacy to its east, around the Nakdong River valley.

King Geunchogo (346–375) expanded Baekje's territory to the north through war against Goguryeo, while annexing the remaining Mahan societies in the south.

Baekje also became a sea power and continued mutual goodwill relationships with the Japanese rulers of the Kofun period, transmitting continental cultural influences to Japan.

The Chinese writing system, Buddhism, advanced pottery, ceremonial burial, and other aspects of culture were introduced by aristocrats, artisans, scholars, and monks throughout their relationship.

In 538, King Seong moved the capital to Sabi (present-day Buyeo County), and rebuilt his kingdom into a strong state.

Temporarily, he changed the official name of the country as the Nambuyeo (남부여; 南扶餘; Korean pronunciation: [na̠m.pu.jʌ̹]; lit.

The location of Sabi, on the navigable Geum River, made contact with China much easier, and both trade and diplomacy flourished during his reign and continuing on into the 7th century.

To memoralize this tragic event in history, a pavilion stands at the so-called "Rock of the Falling Flowers" commemorating Baekje's defeat and the suicide of the kingdom's court ladies and concubines who jumped off the cliff.

They welcomed the Baekje prince Buyeo Pung back from Japan to serve as king, with Juryu (주류, 周留, in modern Seocheon County, South Chungcheong) as their headquarters.

In a case of diglossia, the indigenous Samhan people, having migrated in an earlier wave from the same region, probably spoke a variety of the same language.

[26][27][28] Wooden tablets dated to the late Baekje era have been discovered by archaeologists, and some of them involve the rearrangement of Classical Chinese words according to native syntax.

Delicate lotus designs of the roof-tiles, intricate brick patterns, curves of the pottery style, and flowing and elegant epitaph writing characterize Baekje culture.

To confront the military pressure of Goguryeo to its north and Silla to its east, Baekje (Kudara in Japanese) established close relations with Japan.

[citation needed] Other historians, such as those who collaborated on 'Paekche of Korea and the Origin of Yamato Japan' and Jonathan W. Best, who helped translate what was left of the Baekje annals,[35] have noted that these princes set up schools in Yamato Japan and took control of the Japanese naval forces during the war with Goguryeo, taking this as evidence of them being more along the lines of diplomats with some kind of familial tie to the Japanese imperial family and as evidence against any hostage status.

Recently in 2008, Japan has allowed controlled limited access to foreign archaeologists, but the international community still has many unanswered questions.

"[36] In any case, these Koreans, diplomats and royal relatives or not, brought to Japan knowledge of the Chinese writing system, Buddhism, iron processing for weapons, and various other technologies.

[40] According to mythical accounts in the controversial Nihon Shoki, Empress Jingū extracted tribute and pledges of allegiance from the kings of Baekje, Silla, and Goguryeo.

Also complicating the matter is that in the Nihongi a Korean named Amenohiboko is described in Nihon Shoki as a maternal predecessor of Tajima-no-morosuku (但馬諸助),[46] This is highly inconsistent and difficult to interpret correctly.

[41][47][48] The Nihon Shoki is widely regarded to be an unreliable and biased source of information on early relations with Korea, as it mixes heavy amounts of supposition and legend with facts.

In the project of writing a common history textbook, Kim Tae-sik of Hongik University (Korea) denied Japan's theory.

The former royal family members were initially treated as "foreign guests" (蕃客) and were not incorporated into the political system of Japan for some time.

Baekje is believed to have introduced the man'yōgana writing system to Japan, of which the modern hiragana and katakana scripts are descendants.

[60] Baekje Historic Areas, which feature locations with remains of the period, was designated a UNESCO World Heritage site in 2015.