Tsuda Sokichi(津田左右吉) is a remarkable historian given the ambivalence of historiography of colonialism, which not only historically defended invasion and colonization, but also tried to reorganize East Asian history centered on Japan. Having had an idea of contempt for China and Korea, he talked about the purity of the Japanese imperial family and the uniqueness and excellence of the Japanese people and culture based on it. In this process, like other Japanese historians, he affirmed Japan’s conquest and domination of Korea in ancient times. As is well known, Tsuda viewed Kojiki(古事記) and Nihonshoki(日本書紀) as the same as a literary work. Therefore, he didn’t believe the Empress Jingu(神功皇后)’s conquest of Silla, which was recorded in Nihonshoki. However, what he denied was Empress Jingu, not the Silla conquest. In other words, the conquest of Silla by the Yamato sovereignty is a historical fact, but it was not Empress Jingu who conquered Silla. He argued that it was in the late 4th century that the Yamato sovereignty’s conquest of Silla based on the Gwanggaeto monument.
However, in order to talk about the conquest of Silla by the Yamato sovereignty in the late 4th century, it was necessary to explain the growth of the Yamato sovereignty. This is because achieving overseas conquest and domination means that political power emerged and developed early in Japan, and culture blossomed for it. Tsuda found the main cause of the emergence and development of political power in ancient Japan before the 8∼10th centuries when Japanese culture reached the level of confrontation with Chinese culture, from the influx of Chinese culture into Japan. Lelang Commandery(樂浪郡) and Daifang Commandery(帶方郡), which were established in the northwest of the Korean Peninsula in the 1st century B.C. and existed until the early 4th century, were the starting points to explain this. The small powers of the Tsukushi(筑紫) region, which is advantageous for transportation to the Korean Peninsula, accepted Chinese culture from Lelang Commandery and spread it to the Kinki(近畿) region, and by the second century, Yamato Rowing also grew into a significant power and subsequently conquered surrounding powers. In the 4th century, the weakening of the Chinese dynasty caused by the Xianbei(鮮卑)’s activities led to the disappearance of the Lelang and Daifang Commanderies, the supporters of the Tsukushi region. And this was an opportunity for the Yamato sovereignty to occupy this area. On the other hand, in the southern region of the Korean peninsula, which remained at the tribal state under the pressure of the two Chinese commanderies, when the two commanderies disappeared, Silla unified the small country in Jinhan(辰韓) region and put pressure on the Byunhan(弁韓) region. Then, Byunhan’s powers asked Yamato for help, as a result, Yamato sovereignty’s conquest of Silla took place in the late 4th century. This was a historical image, which Tsuda drew through Japan’s conquest of the Korean Peninsula in ancient time. Presenting this historical image, Tsuda cited the existence of the monarch of the Yamato sovereignty, the imperial family of Japan, as one of the reasons for the growth of the Yamato power, in addition to the changes brought about by the influx of Chinese culture through Tsukushi and the activities of Xianbei. In other words, the historical image presented by Tsuda was to explain Japan’s history of the growth and development of the Yamato sovereignty centered on the imperial family with East Asia as the stage.