Battle of Vinh Yen
Following the 1950 Viet Minh successes against a fixed line of fixed forts, the Viet Minh began a series of attacks in the Hanoi area, which came to be known as the Battle of Vinh Yen. They were a severe reverse for Vo Nguyen Giap and his forces, and were an early example of how the Communist forces had to learn to avoid engaging their enemies in a manner where the enemy had a technological superiority. After a time, the Viet Minh, and its successors, developed techniques for defeating an apparent technical superiority, as at Dien Bien Phu. In later wars of Vietnam, they learned to cope with the failures to effectively use technology at the Battle of Ap Bac, took heavy casualties but acquitted themselves well at the Battle of the Ia Drang. It remains convroversial if Giap really intended to repeat Dien Bien Phu at the Battle of Khe Sanh, or if that was a diversion as part of a larger campaign. Nevertheless, Khe Sanh was not a military victory, although it may have been part of a political victory.
In the Vinh Yen area, attacks, on January 13, went well. On the 14th, however, Jean de Lattre de Tassigny took personal command, called for the airlift into his area of troops 1000 kilometers away, and gathered every aircraft — combat or trainer — that could carry napalm. Viet Minh forces, in the open and without anti-aircraft artillery, came under the heaviest air attacks that the French ever delivered. It cost them over 6,000 men. 
Viet Minh caught by air power
Fall quotes a Viet Minh officer,
However, all of a sudden, hell opens in front of my eyes. Hell comes in the form of large, egg-shaped containers dropping from the first plane, followed by other eggs from the second and third planes. Immense sheets of flmes, extending over hundreds of meters, it seems, strike terror into the ranks of my soldiers. This is napalm, the fire which falls from the skies.
As the oficer fell back, he urged a platoon commander to hold the French as long as possible while he reformed his troops. The junior officer's eyes were wide with terror "What is this? The atomic bomb?"
"No, it is napalm." urging one of his platoon commanders to hold the advancing French infantry, while under air attack.
On 23 March, Giap tried again, striking at the Hanoi area from the east, across the Day River, towards Haiphong. This time, the French did not meet his open forces with air power, but with the fire from naval forces from the river. 
Political effects on the Viet Minh
- Fall, Bernard B. (1972 (4th edition copyright 1967)), Street without Joy, Shocken, pp. 36-37
- Fall, p. 39-40
- Currey, Cecil B. (2005), Victory at Any Cost: The Genius of Viet Nam's Gen. Vo Nguyen Giap, Brassey's, Currey, pp. 172-174