The Battle of Dong Khe was a battle fought between the French Far East Expeditionary Corps and the Viet Minh during the French Indochina War. It took place in Dong Khe, in the Province of Tonkin, Vietnam, from September 15 to September 18, 1950, ending with a Viet Minh victory.
As the Colonial Route 4 was a vital supply line that provided the Viet Minh with weapons and ammunition from China, the commander of the Viet Minh forces, Nguyen Giap, wanted to hang on to this important route at whatever cost. In order to avoid a future French attack aimed at blocking this supply line, he deemed necessary to capture the French outpost of Dong Khe. When more Chinese weapons and communist troops had arrived in Tonkin, crossing the border of northern Vietnam by june 1950, Nguyen Giap decided to launch an assault on the French Dong Khe fortress on September 15, 1950. After three days of ferocious fighting, Dong Khe fell in communist hands on September 18.
Having been defeated at the battle of Dong Khe, the French joint Chiefs of Staff wanted to protect the French forces at the Cao Bang outpost. So, they ordered the commander of the French unit deployed there, Colonel Charton, to withdraw 100 km southwards to the town of That Khe. To protect and support their withdrawal, a Foreign Legion battalion, commanded by Colonel Lepage, was sent to the area to meet Charton’s men. On the way back, both units were constantly under attacks carried out by both Viet Minh and Chinese forces, suffering a lot of casualties. Thus this French withdrawal from Cao Bang towards That Khe was hell on earth.