The Lạng Sơn campaign (3 to 13 February 1885) was a major French offensive in Tonkin (northern Vietnam) during the Sino-French War (August 1884–April 1885). The Tonkin Expeditionary Corps, under the command of General Louis Brière de l'Isle, defeated the Chinese Guangxi Army and captured the strategically important town of Lạng Sơn in a ten-day campaign mounted under formidable logistical constraints.