Under the most prominent of the Tây Sơn brothers Nguyễn Huệ Vietnam experienced several years of relative peace and prosperity.

He was successful and forced the Nguyễn lords to abandon some of their conquests, such as the Principality of Hà Tiên on the southernmost coast of Vietnam.

Nguyễn Huệ, the brothers' leader, said that his goal was to end the people's oppression, reunite the country, and restore the power of the Lê emperor in Hanoi.

In 1773 the Tây Sơn captured the port of Qui Nhơn, where the merchants, who had suffered under restrictive laws put in place by the Nguyễn, lent the uprising their financial support.

The Nguyễn, at last recognizing the serious scale of the revolt, made peace with the Siamese, giving up some land they had conquered in previous decades.

However, their problems were compounded when Trịnh Sâm chose to end the 100-year peace and exploit the turmoil in the south by sending his army to attack Phú Xuân (modern-day Huế), the Nguyễn capital.

The Trịnh army captured the city, forcing the Nguyễn to flee to Gia Định (now modern day Saigon).

In 1785, Siam launched an invasion again and occupied part of the Mekong Delta, but was defeated by Nguyen Hue in the Battle of Rạch Gầm-Xoài Mút.

The Qianlong Emperor agreed to restore Lê Chiêu Thống to power, and so in 1788, a large Qing army marched south into Vietnam and captured the capital Thăng Long.

He addressed his troops before the battle saying:[citation needed] The Qing have invaded our country and occupied the capital city, Thăng Long.

In our history, the Trưng Sisters fought against the Han, Đinh Tiên Hoàng against the Song, Trần Hưng Đạo against the Mongol Yuan, and Lê Lợi against the Ming.

[8][1] Anti-pirate activities were undertaken by a joint alliance between the Qing dynasty and Nguyễn lords Gia Long while Chinese pirates collaborated with the Tay Son.

[1] Chinese and Vietnamese sources agreed that Nguyễn Huệ sent an imposter with a delegation to Beijing, where they were received with lavish imperial favors.

[1] The Qianlong Emperor approved the proposal and bestowed Nguyễn Huệ with the title An Nam quốc vương ("King of Annam").

The title indicated that Nguyễn Huệ was recognized as the legal ruler of Vietnam and Lê Chiêu Thống was no longer supported.

[19][20] The Nguyễn executed the defeated Tây Sơn leader Bùi Thị Xuân by crushing the body with an elephant.