While they recognized the authority of and claimed to be loyal subjects of the revival Lê dynasty, they were de facto rulers of southern Đại Việt.

[4] The Nguyễn lords traced their descent from a powerful clan originally based in Thanh Hóa Province.

The founders of both clan Nguyễn Kim and his son-in-law Trịnh Kiểm fled to Thanh Hóa province and refused to accept the rule of the Mạc.

All of the region south of the Red River was under their control, but they were unable to dislodge the Mạc from Đông Kinh ( the capital of state) for many years.

Kim's eldest son Nguyễn Uông initially took power, but he was soon secretly assassinated by his brother-in-law Trịnh Kiểm who assumed control of the government.

Kim's second son Nguyễn Hoàng feared that he would face same fate as his brother; hence, he attempted to flee the capital to avoid further assassination aimed at him.

In March 1568, Emperor Lê Anh Tông summoned Hoàng for a meeting at Tây Đô and met Trịnh Kiểm at his personal mansion.

He arranged for the emperor to additionally appoint Hoàng governor of Quảng Nam province to keep him faithful to Kiểm to join an alliance against Mạc dynasty in the north.

Nguyễn Hoàng slowly expanded his territory further south, while the Trịnh lords continued their war with the Mạc dynasty to control over northern Vietnam.

As a consequence of these events, Nguyễn Hoàng formally broke off relations with the court in the north, rightly arguing that it was the Trịnh who ruled, not the Lê emperor.

When the war with the Trịnh ended, the Nguyễn were able to put more resources into suppressing the Champa kingdoms and conquest of lands which used to belong to the Khmer Empire.

The Dutch brought Vietnamese slaves they captured from Nguyễn territories in Quảng Nam Province to their colony in Taiwan.

The Nguyễn lords established the protectorate of Principality of Thuận Thành to wield power over the Cham court until Minh Mạng Emperor abolished it in 1832.

Inscription on a Nguyễn cannon manufactured by Portuguese engineer and military advisor Juan de Cruz dating from 1670 reads "for the King and grand Lord of Cochinchina, Champa and of Cambodia.

The war ended with a negotiated settlement, whereby Ang Em was allowed to take the Cambodia crown in exchange for pledging allegiance to the Siamese.

The fighting lasted some ten years, but the Vietnamese fended off the Cambodian raids and secured their hold on the rich Mekong Delta.

[17] With Siam embroiled in war with Burma, the Nguyễn mounted another campaign against Cambodia in 1755 and conquered additional territory from the ineffective Cambodian court.

At the end of the war the Nguyễn had secured a port on the Gulf of Siam (Hà Tiên) and were threatening Phnom Penh itself.

After some early success, the Nguyễn forces by 1773 were facing internal revolts and had to abandon Cambodia to deal with the civil war in Vietnam itself.

In 1771, as a result of heavy taxes and defeats[citation needed] in the war with Cambodia, three brothers from Tây Sơn began a peasant uprising that quickly engulfed much of southern Vietnam.

In 1774, the Trịnh in Hà Nội, seeing their rival gravely weakened, ended the hundred-year truce and launched an attack against the Nguyễn from the north.

The new king of Siam, Rama I had more urgent affairs to look after than helping Nguyễn Ánh retake Vietnam and so this campaign faltered.

[19] Quảng Nam Province was the site where fourth rank Chinese brigade vice-commander dushu Liu Sifu was shipwrecked after suffering a storm.

The Vietnamese sent the Chinese Zhao Wenbin to led the diplomatic delegation on the ship and requested the establishment of trade relations with the Qing court.