Dai Viet

Đại Việt ( [ɗâjˀ vjə̀t], literally Great Viet) is the name of Vietnam for the periods from 1054 to 1400 and 1428 to 1804. Beginning with the rule of Lý Thánh Tông (r. 1054–1072), the third emperor of the Lý Dynasty, until the rule of Gia Long (r. 1802–1820), the first emperor of the Nguyễn Dynasty, it was the second-longest used name for the country after "Văn Lang".

Previously, since the rule of Đinh Tiên Hoàng (r. 968–979), the country had been referred to officially as Đại Cồ Việt (); () in the name of Gautama Buddha (瞿曇·喬達摩). The term "Việt" is the same as the Chinese word "Yue", a name in ancient times of various non-Chinese groups who lived in what is now northern/southern China and northern Vietnam ; so it means "Great Buddhist Viet". In 1010 Lý Thái Tổ, founder of the Lý Dynasty, moved the capital of Đại Cồ Việt to Thăng Long (Hanoi) and built the Imperial Citadel of Thăng Long where the Hanoi Citadel later stood.

In 1054, Lý Thánh Tông - the third Lý emperor - renamed the country to Đại Việt. In 1149 the Lý dynasty opened Vân Đồn seaport in the modern north-eastern province of Quảng Ninh for foreign trade.

The Dai Viet successfully stopped attacks by the Khmer Empire, under Suryavarman II, in 1128, 1132 and 1138. A final expedition in 1150 had to withdraw before it could attack.

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