They insisted on sending military to Korea on ground that some scholars of Kokugaku (the study of Japanese classical literature) and Mito-gaku (the scholarship and academic traditions that arose in the Mito Domain), and Shoin YOSHIDA said that ancient Japan had hegemony over Korean peninsula according to "Kojiki" (The Record of Ancient Matters) and "Nihon-shoki" (Chronicles of Japan).
江戸時代後期に、国学や水戸学の一部や吉田松陰らの立場から、古代日本が朝鮮半島に支配権を持っていたと『古事記』・『日本書紀』に記述されていると唱えられており、こうしたことを論拠として朝鮮進出を唱えた。