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Lê Thái Tông (ruled 1433–1442)

Lê Thái Tông (黎太宗, ruled 1433–1442) was the official heir to Lê Lợi. However, he was just eleven, so a close friend of Lê Lợi, Lê Sát, assumed the regency of the kingdom. Not long after he assumed the official title as Emperor of Vietnam in 1438, Lê Thái Tông accused Lê Sát of abuse of power and had him executed. In December 1435, Thái Tông ordered general Tư Mã Tây to subdue the Tày chief Cầm Quý who having a ten-thousand army of raiders in the northwest region.

In January 1436, the emperor ordered to make roads and canals from northwest region to the capital for showing the superior power of the Imperial court to the local tribes men. From 1437 to 1441, tribe men from Ai-Lao crossed the Annamite Range, raided in Thanh Hóa and southern Hưng Hóa (now Sơn La province) with the help of the local raiders led by Nghiễm Sinh Tượng were suppressed by the Imperial army. The Lê dynasty started treating hostilely to the ethnic minorities in western region. On a stone monument that was carved in 1439 under Thái Tông's reign said "Bồn-Man (Muang Phuan) barbarians were against our assimilation, they need to be exterminated to their roots, and with the Sơn-Man (Mường and Chứt) barbaric raiders, we need to eliminated all of them,..."

According to a Mạc – Trịnh version of Complete Annals of Đại Việt, the new Emperor had a weakness for women. He had many wives, and he discarded one favorite after another. The most prominent scandal was his affair with Nguyễn Thị Lộ, the wife of his father's chief advisor Nguyễn Trãi. The affair started early in 1442 and continued when the Emperor traveled to the home of Nguyễn Trãi, who was venerated as a great Confucian scholar.

Shortly after the Emperor left Trãi's home to continue his tour of the western province, he fell ill and died. At the time the powerful nobles in the court argued that the Emperor had been poisoned to death. Nguyễn Trãi was executed as were his three entire relations, the normal punishment for treason at that time.