Đại Việt as an independent state (Annam). On April 15, 1428, Lê Lợi took the throne and claimed himself King of the restored Dai Viet kingdom. He chose his reign name Thuận-Thiên (順天), literally "To obey Heaven." Lê Lợi's proclamation of independence reflected the Sino-Vietnamese tensions as well as Vietnamese pride and patriotism: Reign Lê Lợi formally re-established Đại Việt as the Xuande Emperor of the Ming Empire officially recognized Lê Lợi as the king of Dai Viet in 1431. In return, Lê Lợi sent diplomatic messages to the Ming imperial court, promising his loyalty as a nominate tributary state of China and cooperation, and paid 50,000 gold taels for obtaining investiture. The Ming imperial court accepted this arrangement, much as they accepted the vassal status of Korea under the Joseon dynasty. Lê Lợi briefly established good relations with Champa's king, Indravarman VI (r. 1400–1441). Lê Lợi renamed the capital, Thăng Long, to Đông Kinh, which later known as Tonkin. He embarked on a significant reorganization of the Vietnamese government, based on the old system of government which was developed during late 14th century. He also elevated his longtime comrades and generals such as Nguyễn Trãi, Tran Nguyen Han, Lê Sát, Pham Van Sao, and Trịnh Khả to high official rank. The Le government rebuilt the infrastructure of Vietnam: roads, bridges, canals. Land distribution were awarded to soldiers that contributed in the war against the Ming Empire. He revived the classical examination and devised good administrative laws. With the peace returned, men released from the army service, included non-Viet soldiers, were encouraged to settle in low density areas in the country, increasing rice production led population expansion during his reign, particularly in the coastal areas. From 1430 to 1432, the king and his army fought a set of campaigns in the hills to the west of the coastal area. Then, in 1433, he became sick and his health declined. On his deathbed he appointed his prince Lê Sát as the regent for his second son, who would rule after him as Lê Thái Tông. He was posthumously named as Thái Tổ. Internal palace politics quickly decimated the ranks of Lê Lợi's trusted counselors, Trần Nguyên Hãn committed suicide when he was being taken to the capital for investigating his suspected betrayal, Phạm Văn Xảo was executed in 1432 and Lê Sát, who ruled as regent for five years, was executed