On February 17, 1979, a fierce battle to protect the nation's border and the residents took place at Dong Dang Fortress in Cao Loc District, Lang Son Province, during the northern border defense war.
In that fight, the fortress was attacked by the enemy that used explosives to break the entrances, poured gasoline into the tunnels, and set them on fire. Hundreds of Vietnamese soldiers, police officers, and local people sacrificed their lives during that time.
Dong Dang Fortress, located at Height 339 in Cao Loc District, Lang Son Province, was built by the French colonists between 1936 and 1940 for the northern border defense, blocking key routes such as National Highways 1A, 1B, and 4A that pass through the Dong Dang area in Cao Loc District.
Due to its strategic location, Dong Dang Fortress was designed for observation of Dong Dang Town and the surrounding area near the border as well as key traffic routes passing through the region.
