Gwanggaeto Stele
This period is divided into the Kofun and Asuka period. Ancient Japan had close ties with the Gaya confederacy and Baekje on the Korean Peninsula. Gaya, where there was an abundance of naturally occurring iron, exported abundant quantities of iron armor and weapons to Wa, and there may have even been a Japanese military post there with Gaya and Baekje cooperation.. According to the Gwanggaeto Stele, Silla and Baekje were client states of Japan. The Chinese Academy of Social Sciences investigated the stele and reported that it reads, "Silla and Baekje were client states of Japan".