21°50′52″N 106°45′28″E / 21.84778°N 106.75778°E
Lạng Sơn () is a city in far Northern Vietnam, and the capital of Lạng Sơn Province. It is accessible by road and rail from Hanoi, the Vietnamese capital, and it is the northernmost point on National Route 1.
The Sino-French or Franco-Chinese War, also known as the Tonkin War, was a limited conflict fought from August 1884 to April 1885 between the French Third Republic and the Qing dynasty for influence in Vietnam. There was no declaration of war.
The Qing armies performed better than in their other nineteenth-century wars. Although French forces emerged victorious from most engagements, the Qing scored noteworthy successes on land, notably forcing the French to hastily withdraw from occupied Lạng Sơn in the late stages of the war, thus gaining control of the town and its surroundings. However, a lack of foreign support, French naval supremacy, and northern threats posed by Russia and Japan forced the Qing to enter negotiations.