The 312th Army attacked strongpoints 506 and 507 (Eliane 10), wiping out French troops on the left bank of Nam Rom River.
The 308th Infantry advanced to attack strongpoint 310 (Claudine 4) in Na Noong, and quickly launching an attack towards De Castries' Command Post.
The 304th Infantry stationed a unit in Na Tu to block the road to Laos, preventing the enemy from fleeing.
The Campaign Command decided to quickly complete the missions of the offensive, preparing all favourable conditions for a general attack.
At 20:00 on May 6, 1954, Vietnamese troops concentrated heavy mortar fire on strongpoints on A1 (Eliane 2), C2 (Eliane 4), 506 (Eliane 10), 310 (Claudine 4). In addition to the force of 105mm and 75mm artilleries and 120mm and 81mm mortars, Vietnamese troops for the first time mobilised 12 six-barrel H6 rocket launchers, each firing 72 shots.
During the 45-minute attack, although the French enemy reacted weakly, they were prepared in advance. Right after Vietnamese soldiers stopped firing, all remaining enemy guns of French army in Muong Thanh started pouring bullets into Vietnamese troops’ trenches around A1 (Eliane 2) and C2 (Eliane 4).
In the A1 hill area, at 20:25 on the same day, the Vietnamese soldiers in the trenches who started the assault were ordered to turn their backs against A1 hill, close their eyes, and open their mouths, to protect themselves from the shock wave and flash of the nearly 1-tonne explosives.
Exactly at 20:30, after a deep explosion on hill A1, Regiment 174 divided into several units to attack the top of the hill along the trenches; separating A1 (Eliane 2) from Muong Thanh.
On the French side, they were reinforced with 94 soldiers from the 1st Colonial Parachute Battalion, the command company, and part of the 4th company who parachuted into Dien Bien Phu, including battalion commander Captain Bazin.
Colonel Langlais ordered the Dakota plane carrying Company 1 of the 1st Colonial Airborne Battalion to return to Hanoi.
During the night, General De Castries requested an urgent supply of mortar shells of all sizes. 42 tonnes of goods were dropped as a result, but not a single package was collected.
