Early Japan and the Korean Peninsula

Military Incursions

The nature of the early Japanese role in the Samguk Period remains a subject of debate among Korean, Japanese, and Chinese scholars. What is known of the Japanese involvement comes from a variety of Chinese sources, Korean records including the Samguk Sagi, Japanese histories such as the Nihonshoki, and the Gwanggaeto Stele. While disputed by nationalist Korean scholars, histories indicate that the Japanese made military forays into the southern regions of the Korean peninsula, in the kingdoms of Baekje and Shilla and the territories of the Gaya confederacy. Shilla was recorded to have been attacked by the Japanese at various points. Some Chinese histories record the Chinese emperor bestowing titles to "Kings of Wa (Japan)" for the regions south of Goguryeo as well as clashes between Wa people and the Goguryeo kingdom, which suggest that at some point the Japanese may have made forays onto the Korean peninsula temporarily as both invasion forces and allies of the Shilla and Baekje kingdoms.

Immigration and Shifting Identities

Before identifying with certainty of what is "Japanese" or "Korean" as an actual ethnic/racial identity, it should be noted that cultural exchanges and immigration between the Korean Peninsula and the Japanese archipelago occurred throughout the Samguk Period. The early Japanese aristocracy likely had some connections to the elites of the Korean Baekje and Shilla kingdoms; indeed some of the Japanese rulers were even blood-related to Baekje or Shilla royalty including the legendary Japanese empress, Jingu Kogo, who was said to have led an expedition in the southern Korean peninsula, and Emperor Kammu. Artisans and specialists from both the Chinese and Korean lands immigrated to Japan and utilized their talents for the emerging Yamato court and were highly responsible for the transmission of the advanced technologies and arts of the mainland to the Japanese archipelago. These immigrants' descendants later became integrated into Yamato society. Following Baekje's fall, former aristocrats also migrated to Japan.

Alliances

As Goguryeo rode on its wave of success and expanded rapidly, both the kingdoms of Baekje and Shilla sought to acquire military support from the emerging Yamato state as a means to counteract their dangerous northern neighbor. King Asin of Baekje and King Silseung of Shilla both sent royal hostages to Yamato as a means to ensure military alliances.