Editing Battle of Route Coloniale 4 (section)

==RC4 in the First Indochina War==
During the [[First Indochina War|French Indochina War]] (1946–1954), French forces attempted to re-establish colonial control of [[Vietnam]], while the Vietnamese [[guerrilla warfare|guerrilla]] forces, the communist Việt Minh, led by [[Ho Chi Minh]] fought for independence. Initially the Việt Minh were unsuccessful in dealing with the better -trained and -equipped French forces. Their situation improved in 1949 after the [[Communist Party of China|Chinese]] [[People's Liberation Army]] of [[Mao Zedong]] defeated the [[National Revolutionary Army|Nationalist army]] led by [[Chiang Kai-shek]]. This gave the Việt Minh, now almost completely made up of members of the [[Vietnam Workers Party]], a safe haven for organization and training, as well as an initially sympathetic ally to provide them with arms and [[logistical]] support.

[[Võ Nguyên Giáp]], the military leader of the Việt Minh, launched an offensive against the French in early 1950. From February to April, his operation ''Le Hong Phong I'' developed through the [[Red River (Asia)|Red River Valley]], largely giving the Việt Minh control of northwestern [[Tonkin]], near the Chinese border. The area became a Việt Minh stronghold, except for the RC4 highway.

On 25 May, 2,500 Việt Minh troops overwhelmed the French fortress at [[Đông Khê, Cao Bằng|Đông Khê]], which lay at the strategic center of RC4, thus cutting the supply line between the French positions at Cao Bằng and [[Lạng Sơn]]. French [[paratrooper|paratroops]] retook Đông Khê on the evening of 27 May and a company of [[French Foreign Legion|Legionnaires]] took charge of the fort.

Meanwhile, the Việt Minh regular army grew in size and experience. By the beginning of September, it comprised roughly 100,000 combatants in 70 [[battalion]]s, with another 33 battalions of regional forces (40,000 men) as well as some 60,000 local support personnel. Giap then began harassing French positions along RC4 in northern Vietnam with mines and ambushes. The French responded by dismantling their small posts along the road and concentrating area forces in the fortified positions at Đông Khê and Cao Bằng. Giap planned to launch another assault on French positions in operation ''Le Hong Phong II''.

On 16 September, five Việt Minh infantry and one heavy weapons battalions attacked Đông Khê. It was then garrisoned by some 300 French Foreign Legion troops comprising the 5th and 6th companies of the 2nd battalion of the [[3rd Foreign Infantry Regiment|3rd Regiment]] (3rd REI). On 18 September, the fort was overrun after bitter fighting, and only 12 survivors escaped to the nearby post at [[Thất Khê]]. 140 Legionnaires had been taken prisoner, the remainder being killed or missing in action.

Thất Khê was quickly reinforced by the Foreign Legion's [[1st Foreign Parachute Battalion|1st Parachute Battalion]] (1st BEP), which parachuted in on 17 September. The 1st BEP waited at Thất Khê while a force of French [[Colonialism|colonial]] troops, the [[Morocco|Moroccan]] 1st and 11th [[Goumier|Tabors]], and the 1st Marching Battalion of the 8th Moroccan Tirailleurs Regiment, assembled at [[Lạng Sơn]]. Designated ''Groupement Bayard'' the combined force comprised 3,500 men under the command of [[Colonel]] Le Page. The task force launched an intelligence raid, capturing prisoners who said a massive Việt Minh offensive was planned.

Meanwhile, General [[Marcel Carpentier]], the commander in chief of French Indochina, decided to evacuate Cao Bằng. The commander of the Cao Bằng fort, Colonel Charton, was ordered to destroy his heavy equipment and motor transport and evacuate towards Đông Khê. The plan was that Groupement Bayard would fight its way north from Thất Khê and retake Đông Khê, holding it long enough to link up with the Cao Bằng group. This group comprised 2,600 troops and 500 civilians, the latter mostly pro-French [[Thai people|Thai]] [[Partisan (military)|partisan]]s and their families.