After Ho Chi Minh 's government was established in September 1945 , Japanese had surrendered to the British and Indian Army , under the terms of the Potsdam Conference , to the south of the 16th parallel , while the Chinese Nationalist Party ( the Kuomintang ) . As strategy , Ho Chi Minh entered into an agreement with the French so that he could face any threat from the Chinese and a Franco-Vietnamese agreement was signed . This provided for a free Vietnam within the French Union and the Indochinese federation . However , the French launched an offensive against the Viet Minh in October 1947 with Lạng Sơn as a their base . However , the Viet Minh managed to thwart the French Offensive and forced the French to withdraw to Lạng Sơn . However , the Viet Minh pursue the French Army , they had a very decisive victory on Highway 4 and they had to finally withdraw from Lạng Sơn . This marked the beginning of First Indochina War In 1950 the Viet Minh took control of the province and the town . During February 1979 , the Chinese invaded Vietnam through the border town of Don Dong ( to the north of Long Son town ) . In this war , which lasted for five days , 600,000 soldiers had descended on Vietnam ; Lạng Sơn town was the major town that received the major thrust of 200,000 soldiers from China and occupied the capital city of the Northern Province . However , the Vietnamese had the last say as the Vietnamese army was successful in defeating the Chinese army , which bid a hasty retreat . This has achieved the status of a folk lore in the province . The frontier village , which became famous during the war with China , has remnants of the war on display to the visitors . However the border has been rebuilt and brisk trade flourishes between Vietnam and China through this town . During the Chinese invasion in 1959 the Lan Son town was also severely damaged , however it has been rebuilt since then . The old part of the town , near the Kyu Kung River has some interesting historical sites
Potsdam Conference
Potsdam Conference
Lạng Sơn Province