French troops advancing to occupy Lang Son,…
June 1884 CE
French troops advancing to occupy Lang Son, in accordance with the terms of this agreement, clash near the small town of Bac Le with a detachment of the Chinese Guangxi Army on June 23, 1884.
The Chinese open fire on the advancing French, precipitating a two-day battle in which the French column is seriously mauled.
This incident, the Bac Le Ambush, is the proximate cause of the Sino-French War.