state." In 1973, Minoru Katakura used the term "centralized feudal system" to describe the Lý dynasty's Viet state. Yumio Sakurai reconstructed the Lý dynasty as a local dynasty, that the dynasty was only able to control several inner areas, while outer areas (phu) were autonomously governed by local clans of various ethnolinguistic backgrounds, who aligned to the royal clan through Buddhist alliances, such as temples. The Viet king "man of prowess" was the center of the mandala structure that has influences beyond the Red River Delta via Buddhist alliance with local lords, while a bureaucracy was still practically nonexistent. For examples, an inscription dating from 1107 in Hà Giang records the religious-political connection between the Nùng Hà clan with the dynasty, or another inscription dated 1100 commemorates Lý Thường Kiệt as the lord of Thanh Hoá. As a mandala realm, according to F. K. Lehman, its direct territories could not exceed more than 150 miles in diameter, however, the Đại Việt kingdom was able to maintain a large influence sphere due to active coastal trade and maritime activities with other Southeast Asian states. Trần-Hồ period During the 13th and 14th century as the Trần dynasty ruled the kingdom, the Trần first move was preventing matrilineality clans to take over the royal family, by adopting the king–retired king relation, which the emperor usually abdicated in favor of his eldest son while retaining power behind the scenes, and practicing consanguine marriage. To prevent maternal families’ influences, Trần kings took only queens from their dynastic lineage. The state had been more centralized, taxes and bureaucracy appeared, chronicles were written down. Most power is concentrated in the hands of the emperor and the royal families. In the lowland, the Trần removed all non-Trần, autonomous aristocratic clans from the power, appointed Trần princes to rule these lands, tightened up relations between the state and locals. Working in Trần princely lands were serfs-poor peasants that own no land and slaves. Large hydraulic projects that mobilized more labors such as Red River Delta’s dyke system were constructed-one that maintained and increased its particularly wet-rice-based agricultural economy and its population by diverting rivers to aid in irrigation. Confucianism was ensured by the Trần monarchs as the second belief, gave rise to the literati class, which later became rivals to the established Buddhist clergies. The Việt monarchy during this period faced a series of massive Yuan and Cham invasions,