Vietnam in the XIII century: The feudal government of Vietnam at that time was a centralized government, rather than a scattered one like many European countries. It is not the same with Song Dynasty's centralized government. After ending the chaos at the end of the Ly Dynasty, the Tran Dynasty built a strong centralized government. The life of the people is stable, the production level is highly developed. By the time the Mongol Empire waged an invasion war, the conflict between the Dai Viet feudal class and peasants was still delayed, not yet developed to a fierce level. Facing the war of aggression of the enemy, the Dai Viet feudal class united the entire people to stand up for the resistance to save the country. This book recounts the three wars against the Mongols of Dai Viet, all three times winning and defending the country.