An interesting article about the unification of the three kingdoms of Goguryeo.

 It is based on Professor Kim Yong-man's opinion. And the content is not a hypothetical version of Goguryeo's unification of the three kingdoms, but I will write an explanation of why Goguryeo did not unify the three kingdoms. According to the contents of the heavy rain or Jungwon Goguryo Monument excavated from the Gyeongju Houchong Tomb, "I will keep the order of heaven by harmonizing with each other as the king of Goguryeo and the hawk of Silla forever." This can be seen as an expression of Goguryeo's strong will to integrate Silla. During the reign of King Hotae and King Jangsu, which were the foremost periods of Goguryeo, Silla was completely a kingdom of Goguryeo and Baekje had a military god relationship. But Baekje was still a powerful country. After King Asin's defeat to King Hotei, Baekje regained its national power for the first time in more than 20 years and resumed diplomacy with China against Goguryeo. I mean, it's a country with strong basic power. And the other thing is that Goguryeo and Baekje both had the legitimacy of Jumong's deficit, and Silla had the legitimacy of Samhan's royal family and maintained the country for hundreds of years, so they didn't want the country to collapse. So they formed the Naje Alliance, and in order for Goguryeo to take over the two countries, they had to put in a lot of troops. Third, due to the geographical location of Goguryeo, it was not possible to deploy many troops to the south. The fourth is a realistic situation. Third, for the same reason, I think it was a wiser judgment to take the lead in the world while reigning as a strong person in reality rather than putting too much energy into the unification of the three countries. Silla called for the unification of Samhan and wanted to completely eliminate Goguryeo and Baekje forces, and that's what happened, because from the standpoint of a weak country, it thought that eliminating the threat to its own country was the only way to survive. For Goguryeo, Silla and Baekje were not threatened enough to destroy the country, so the two countries' views on reunification were so wrong. In addition, even though Goguryeo was able to invade mainland China, not the Three Kingdoms, during its heyday, I will explain why it did not do so, but rather moved toward the Korean Peninsula. To begin with, it is because of Goguryeo's unique view of the world. The Chinese civilization is a total of civilizations created by the Han people in the middle of the Chinese continent. In thousands of years of history, less than half of the Han's total control of China politically and militarily. However, Hun, Seonbi, Malgal, Yeojin, and Mongolia, which dominated the Han people, only took political control, but civilizationally and culturally, they fell into the melting pot of the Han people and lost their identity. Nomads usually invade mainland China for six reasons. First, when the climate became dry or cold, secondly, when food was scarce, thirdly, when agricultural communities interfered with their trade, and fourthly, when the fifth monarch resisted being incorporated into the world order as a means of strengthening his kingship. But Goguryeo didn't have to invade them except for the fifth means of strengthening their kingship. And Goguryeo did not seem to have crossed the Great Wall because it had concerns that it might lose its identity in retrospect.