Trịnh Tạc was one of the most successful of the Trịnh Lords who ruled northern Vietnam. During his rule, he made peace with the Nguyễn, ending the long war. Trịnh Tạc also captured the last small province of Vietnam ruled by the Mạc Dynasty.
Takes control 
Trịnh Tạc took control of the Vietnamese government at a time when things looked bleak. The long war with the Nguyễn Lords was going badly (see the Trịnh–Nguyễn War for details). The Trịnh armies had suffered several defeats under his father, Trịnh Tráng, and the Nguyễn armies had pushed north all the way into Nghệ An province. Trịnh Tạc took over in 1654 and one of his armies was also defeated by the Nguyễn. However, the next year, Trịnh Tạc’s army was victorious and the Nguyễn were driven all the way back to their original provinces in the south. The Royal (Trịnh) army attacked the great defensive walls of the Nguyễn but without success.
Cao Bằng Province 
For the next five years, the war with the Nguyễn was put on on hold while Trịnh Tạc turned his attention to Cao Bằng Province. This was the last bit of Vietnam where the Mạc Dynasty rulers still held power. Periodically they had raided into north Vietnam. The Trịnh had been prevented from the final destruction of the Mạc because they were protected by the Ming Dynasty. But now the Ming had fallen, replaced by the Manchu, and as a result, the Mạc no longer enjoyed the same relationship with the Chinese government. The Mạc made the mistake of siding with a disloyal governor and so the Kangxi Emperor (Khang Hi Hoàng đế) withdrew his protection of the Mạc. In 1667, Trịnh Tạc defeated the Mạc army and drove them out of Cao Bằng Province.
Further conflict 
In 1672, one last effort was made to break the walls of the Nguyễn. For seven months, the Royal (Trịnh) army besieged the Nguyễn walls but, like the previous efforts, the attacks failed. In 1673, Trịnh Tạc and Nguyễn Phúc Tần came to an agreement. Peace finally came to northern Vietnam. This peace between the Nguyễn and the Trịnh was to last for the next 100 years.
The Mạc invaded northern Vietnam from their new base in southern China in 1677 but this invasion was defeated by the Royal (Trịnh) army. Trịnh Tạc died in 1682, leaving the government in the hands of his son, Trịnh Căn.
Death and legacy 
In dynastic matters, Lê Than Tông, the man who was king twice, finally died in 1662. He was succeeded by Lê Huyen Tông. Ten years later, he died and was succeeded by Lê Gia Tông. The new Lê king died after just three years in office (1676) and so he was replaced by Lê Hy Tông.
With the war ended, Vietnam was peaceful and prosperous, Trịnh Tạc had rescued the situation, even though he failed to conquer the Nguyễn.
|Ruler of Vietnam