Feudal Period

In 905, Khúc Thừa Dụ's revolt freed Vietnam, breaking the power of the foreign Tang rulers. After Khúc, Ngô Quyền succeeded him in the defense of the country. After quelling the rebellion of 12 vassals, Ðinh and Lê dynasties had reunited the country and defeated the foreign invaders. Dynasties emerged, each staying in power for varied lengths of time; the Lý, Trần, Hồ, Lê, Mạc, Trịnh and Nguyễn dynasties saw the north-east region undergo numerous changes.

 Important Events:
1.Three great victories against invaders on the Bạch Đằng  River: At three different points in history, aggressors were defeated at this site: Ngô Quyền against the Nam Hán army, Lê Ðai Hành against the Sing and Trần Hưng Đạo against the mighty Mongols.

The first time: Ngô Quyền against the Nam Hán army in 938
 In 937, taking advantage of the power vacuum in Vietnam, Lưu Cung, King of Nam Hán, ordered his son Hoằng Thao to lead a big fleet of warships to invade Vietnam. Lưu Cung himself went by roadway for reinforcements.
 Ngô Quyền and his generals mobilized the local populations in the northeast region to fell trees and make steel-tipped stakes. These stakes were planted in the bed of Bạch Đằng  River. In October 938, hundreds of ships of the enemy under the command of Vạn Vương Hoằng Thao reached the mouth of Bạch Đằng  River. Ngô Quyền sent several small boats to lure them upriver past the stakes into an ambush. At low tide, Ngô Quyền ordered his troops to counterattack. The enemy ships retreated, but got impaled on the stakes. Most of enemy troops, including Hoằng Thao were annihilated. On hearing the news, Lưu Cung felt grief-stricken and never thought of invading Vietnam again.

 The second time: Lê Hoàn against the Song in 981
 The Song King sent 30,000 troops to invade Vietnam in the roadway and seaway. Commander of the roadway troops was Hầu Nhân Bảo. The seaway troops were commanded by Lưu Trừng and Giã Thực. They would go to Vietnam via the Bạch Đằng  River. Lê Hoàn, who had just come to the throne at the will of the whole people, ordered his troops to make and drive large, wooden, steel-tipped stakes into the river bed. Enemy troops were ingeniously lured into the trap and defeated. Meanwhile, Hầu Nhân Bảo was killed in an ambush. Of the enemy generals who could escape, Tôn Hoàn Hưng was beheaded in a market. Lưu Trừng and Giã Thực were imprisoned until death.

 The third time : Trần Hưng Đạo against the mighty Mongols in 1288
The Yuan-Mongolian troops, from the most powerful empire at that time, conquered all the area of Russia, Central Asia, Middle and Near East, and China. They invaded Vietnam two times in 1258 and 1285, but faced failure.
This was the third time. Under the command of Thoát Hoan, their troops entered Vietnam in three directions: the roadway troops came from Yunnan and Guangxi, and from Guangdong by seaway under the command of Ô Mã Nhi and Phàn Tiếp. Trần Hưng Đạo, commander of the Trần Dynasty’s troops chose the seaway his strategic direction. 
Vietnamese troops laid ambush right in the border. On 20 December 1287, Nhân Đức Hầu Trần Toàn won the first battle at Mũi Ngọc. However, the enemy outnumbered our troops, therefore they could continue advancing. General Trần Khánh Dư failed to check their advancing and was subjected to a sentence. He asked the Trần King for giving him a chance to record an exploit in compensation for his fault. Then, Trần Khánh Dư laid an ambush from Vân Đồn to Cửa Lục in Bái Tử Long, Hạ Long Bay. The enemy fleet carrying food escorted by Trương Văn Hổ’s warships came into the ambush and were annihilated. Dư’s troops caught a lot of food. This forced the enemy troops in Thăng Long citadel, which were faced with the scorched earth policy of the Trần Dynasty, to withdraw.
Foreseeing this, Trần Hưng Đạo or Trần Quốc Tuấn emulated Ngô Quyền’s brilliant tactics and had steel-tipped wooden stakes planted in the Bạch Đằng  riverbed. In doing so, he asked an old woman living by the Rừng wharf about the time of high and low tide of the river. General Trần Hưng Đạo’s troops lured the enemy troopships upriver at high tide and then counterattacked at low tide. Enemy soldiers tried to escape ashore, but they were annihilated by our fighters in Hà Nam field. Prior to that, Trần Quốc Toản directed his troops to destroy all bridges in Đông Triều, forcing the escorted troops commanded by Trình Bằng Phi to come back and join Thoát Hoan’s troops. Without reinforcements and rescue, the troopships were killed and captured alive. Enemy generals Ô Mã Nhi, Phàn Tiếp, and Tích Lệ Cơ were beheaded in front of King Thái Tông’s tomb in Long Hưng (Thái Bình), where temporarily housed the Trần court.
The Bạch Đằng  River still retains legends and vestiges. Many local people who had merit are worshipped and honoured. In Vân Đồn there stands the temple dedicated to the locals of Vân Hải who had exploits.
2. In addition, under the Lý Dynasty, Lý Thường Kiệt also advanced his men through this region to overthrow the Sing army.
3. The opening of Vân Đồn Port saw prosperous years through the Lý and Trần dynasties.
4. The birth and development of Trúc Lâm Buddhism from Yên Tử Mountain during the Trần Dynasty was a significant point in the area’s history.