On the night of the 30th day of the Lunar New Year (January 25, 1789), Emperor Quang Trung (Nguyen Hue) led the Tay Son army on a rapid march northward from Phu Xuan (Hue). In just 5 days and nights — from the 30th to the 5th day of the New Year — he annihilated 290,000 Qing troops under Sun Shiyi's command, liberated Thang Long, and expelled all invaders northward. This was one of the most swift and brilliant military campaigns in Vietnamese history.
The background: after the Le dynasty collapsed, Le Chieu Thong appealed to the Qing for help. Emperor Qianlong sent Sun Shiyi with a massive army to 'restore' the Le dynasty, actually intending to annex Dai Viet. The Qing forces occupied Thang Long and comfortably celebrated the Lunar New Year there. Nguyen Hue quickly proclaimed himself Emperor Quang Trung at Phu Xuan on December 25, 1788 (lunar calendar) and immediately set out with his army.
Quang Trung's tactic was to concentrate forces, strike fast and decisively, not allowing the enemy time to reinforce one another. At the Battle of Dong Da (5th day of the New Year), the Tay Son forces used 'fire battle' tactics — burning enemy fortifications — throwing the Qing troops into panic and causing a rout. General Sầm Nghi Đống took his own life; tens of thousands of Qing troops were killed or drowned fleeing across the river. Sun Shiyi abandoned his imperial seal, gold, silver, and military supplies in his desperate flight home.
The Battle of Dong Da — the Spring of 1789 — is a symbol of the Vietnamese people's indomitable spirit and extraordinary military genius. Emperor Quang Trung was not only a brilliant military commander but also a progressive reformer: he promoted the development of Chu Nom (Vietnamese script), reformed taxation, encouraged agriculture, and boosted trade. Sadly, he died suddenly in 1792 at age 39, leaving many of his ambitions unrealized.
Today, the Dong Da Festival is held on the 5th day of the Lunar New Year at Dong Da Mound (Quang Trung Ward, Dong Da District, Hanoi) — commemorating the historic battle and serving as one of Hanoi's most distinctive traditional festivals at the start of each new year. A statue of Emperor Quang Trung stands prominently at the center of the memorial site, facing south — the direction from which his swift army advanced.