During the age of Korea's Three Kingdoms, the peninsula was divided among the kingdoms of Koguryo, Paekche, Silla, and the confederated walled-town states known as the Kaya Federation. The original Paekche state emerged as a kingdom by incorporating various town states in the Han River basin under a centralized, aristocratic rule. It evolved as a feudal system controlling some 22 provinces and districts, each ruled by a prince or other member of Paekche's royal families. Paekche reached its final structure as a centralized, aristocratic state in the middle of the 4th century AD under the reign of the formidable warrior King Kun Ch'ogo.
In 364 AD, stories began to reach the Paekche capital at Wiryesong that described the existence of an "honorable country" far to the east that had long been communicating with the Kaya Federation. Such stories piqued King Kun Ch'ogo's interest to such a degree that he dispatched a scouting party to the Kaya territory to gather information about this mysterious land of the East and how to get there. Later that year, three Paekche envoys traveled to the Kingdom of Tak-sun in the Naktong River basin. During their meeting with the Tak-sun king, they described Paekche's interest in journeying to this eastern land and graciously requested directions. The king admitted that he had, "always heard that there is an honorable country in the East," but added that he had no contact with it, and had no idea how to get there. Noting the three men had no ships, he said, "Even if there were a regular crossing-place, how could you arrive there?" After suggesting that Paekche would need large ships for such a venture, the three envoys returned to Paekche to prepare ships for the journey. Paekche would have to wait to make contact for another time.
Five years later, in 369 AD, Paekche made another expansive military strike to the south. King Kun Ch'ogo and his son, Crown Prince Kun Kusu, led a major attack that overran the city-states of the Ma-han and took control of a sizeable portion of western and southwestern Korea, including all the modern provinces of Kyonggi, Ch'ungchong, and Cholla, as well as parts of Hwanghae and Kangweon. The Paekche kings, father and son, met Prince Homuda, princes Areda and Kaga, and generals Kutyo, Sa-paek, Kaero, Sasa Nokwe, Mong-na Kun-cha, and others at the village of Wi-niu to congratulate them on their successes in the Ma-han campaign.
Prince Homuda, an influential member of a Paekche royal family and a military leader close to King Kun Ch'ogo, had sometime earlier given thought to finding new territory where he could carry on the government of his kingdom in peace. He spoke with other members of the Paekche royal family about his plans to conquer an eastern land, "a fair land encircled [on] all sides by blue mountains." The Imperial Princes, who had similar ideas, agreed. King Kun Ch'ogo chose Prince Homuda to lead the Imperial Princes and a naval force on an expedition against the mysterious land to the East. After rebuilding his command with choice Paekche troops and with the blessings of King Kun Ch'ogo and a "solemn declaration of alliance," Prince Homuda marched east toward the Kaya territory, located a "port of passage" in the southernmost Kaya state of Imna, and set sail for a New World.
In the winter of 369 AD, Prince Homuda's expeditionary force landed on the northern shore of Kyushu at Hakata Bay on the westernmost of Japan's large islands. On the rich agricultural plain near the present site of Fukuoka, the new arrivals from Paekche established a foothold and began building settlements. They spent the next three years repairing and refitting ships, making weapons, training, storing provisions and getting ready to subdue the territory. Prince Homuda's army pushed eastward for six years, encountering fierce resistance from many of the clans in its path. After subduing its opposition by surrender,outright conquest, or death, the expeditionary force finally halted on the rich agricultural plain formed by the Yodo and Yamato Rivers at the head of Osaka Bay. Having gained control over the central part of the country, Prince Homuda proclaimed the creation of his new kingdom, taking its name from the surrounding region and giving the country its first official "name" - Yamato.
Prince Homuda, founder of the Imperial Clan, was enthroned in 390 AD, with an imperial title befitting his stature - King of Yamato. Until the mid-7th century, the word "Yamato" was written as "Wa" (a term used by Chinese historians), but read as "Yamato." The great flowering of Japanese history began on the Yamato Plain and in the area of the Nara Basin, where the emergence of the Yamato Kingdom set a foundation for future Japanese civilizations. As late as the 3rd century AD, there were no horses in Japan. The formal arrival of horses in Japan occurred in 404 AD, when the King of Paekche sent A-chik-ki with a stallion and a mare as tribute. A-chik-ki cared for the two horses in stables on the slopes of Karu, a site that became known as Mumaya-saka (Stable Hill). Thus, the horse eventually bred by the Japanese was not a local horse, but a breed introduced into Japan from Korea.
A nearly continuous flow of people from Paekche and surrounding kingdoms followed in the wake of Prince Homuda's expedition, sailing the Tsushima Strait to Hakata Bay. From around 400 AD, the Yamato Plain and Nara Basin were settled predominantly by immigrants from Paekche, as royal families, generals and their descendants staked their claims in the new land by building palaces and capitals. Many of these clans gained sufficient economic and military power to control to enjoy a hegemony over the surrounding aristocracies that made them both wealthy and powerful. During this period, the Yayoi culture dissolved into the newer Yamato culture as political alliances and outright conquest gradually brought about a loose-knit unity that coalesced most of western Japan into a nation
The Korean and Chinese clans that established roots in Japan were far more sophisticated than the native Yayoi culture and had knowledge, skills and technologies associated with a more advanced civilization. The Yayoi faced a markedly militaristic people with an appetite, if not fondness for warfare. Although the Yayoi jealously clung to the belief they were descendants of native gods, their primitive society underwent a radical change as it absorbed and adapted itself to a higher type of culture
The cultural linkage among China, Korea and Japan produced a considerable amount of interchange among the Chinese of the Lolang Commandery, the people of Paekche and the Kaya Federation, and the inhabitants of Kyushu and islands in the Tsushima Strait. Envoys from Paekche visited Yamato as early as 367 AD and diplomatic embassies between Paekche and Yamato continued almost every year up to the death of King Kun Ch'ogo in 375 AD. His son and successor, Kun Kusu, continued this close relationship with Yamato Japan, cultivating friendships with Jin China on the one hand and Yamato Japan on the other. Because of the natural, intimate relationship between Paekche and Yamato, successive Yamato rulers maintained and administered a port facility in the Imna area (Mimana in Japanese) at the southern tip of the peninsula to serve as a direct short-cut crossing route to Japan. Kaya became a stopping off point for the many Yamato trade missions that traveled between Japan and the Lolang Commandery along the Taedong River. The Yamato who lived in Imna were neither colonists, nor conquerors, but agents who operated by permission from the King of Kaya, who restricted them to the immediate area of the port.
Reference; Korean History
