April 11, 1954: Hill C1 was divided in two, with each side occupying half

Both the Vietnamese and the enemy put all their efforts into consolidating their foothold on the hill, where bombs and bullets destroyed all combat fortifications and hiding places.

Vietnamese soldiers had to retreat to the old line for defence. The 98th Regiment, which was on defensive duty at Hill C1, was also reinforced with by 888th Battalion under the 176th Regiment. On the afternoon of April 11, 1954, the 811th Company under the 888th Battalion was sent to defend, replacing the units that had fought for two days. From this point, the 811th Company under the 888th Battalion took charge of defensive mission at Hill C1 for 20 consecutive days until Vietnamese forces completely destroyed this fortress.

The French army also had to send the third company of the second Foreign Legion Parachute Battalion, which had just arrived at Muong Thanh to replace the exhausted force that fought from the night of April 10 to dawn of April 11, 1954.

By the night of April 11, 1954, Vietnamese troops continued to counterattack but were still unable to capture the flagpole area. Hill C1 was divided in two, with each side occupying a half. The Vietnamese army and the enemy understood each other so well that the two sides agreed to temporarily maintain the situation. Sometimes, there were grenades, bursts of machine gun fire and streams of flamethrowers back and forth. Several assaults took place in a wink.

On the same day, General Vo Nguyen Giap, Commander-in-Chief of the Vietnam People's Army, sent a letter to the officers and soldiers of the 9th Regiment under the 304th General Command, who were participating in eliminating bandits in the northern mountainous area. The General extended compliments to all officers and soldiers of the regiment and announced that one of the enemy's plots was to attack transportation routes to cause difficulties for the Vietnamese army in supplying, supporting, and reinforcing, especially as the rainy season was approaching. General Vo Nguyen Giap assigned the 9th Regiment the mission of maintaining the transport route and ensuring smooth roads, thus contributing to the victory of the Campaign.