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.

From February to April, his operation Le Hong Phong I developed through the Red River Valley, largely giving the Việt Minh control of northwestern Tonkin, near the Chinese border.

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.

The task force launched an intelligence raid, capturing prisoners who said a massive Việt Minh offensive was planned.

The commander of the Cao Bằng fort, Colonel Charton, was ordered to destroy his heavy equipment and motor transport and evacuate towards Đông Khê.

However, Giap had concentrated ten battalions around Đông Khê, reinforced by a complete artillery regiment, together with the remaining forces from Le Hong Phong I.

Le Page renewed the attack on 2 October, pushing west to bypass Đông Khê as Việt Minh numbers were overwhelming.

Meanwhile, Colonel Charton's group, led by the 3rd Battalion, 3rd REI, left Cao Bằng on 1 October; contrary to orders he took with him his heavy equipment.

After bitter fighting, they finally abandoned their heavy equipment and linked up with Groupement Bayard in the hills around Đông Khê on 5 October.

Martin Windrow notes that "Some 130 of the Legion parachute battalion out of the 500 that had jumped emerged from this breakthrough fight; they had only escaped by clambering down lianas shrouding a 75 ft cliff with their wounded tied on their backs".