What are the causes of the battle Dien Bien phu?

For close to ten years, the French had been fighting the Viet Minh. The last year of the war, 1954, the French military decided to establish a base in an area that would interrupt the communist supply system and at the same time draw them into a "set piece" (conventional) battle that would destroy them. The area selected was Dien Bien Phu, located in the former North Vietnam. Rule number #1: NEVER underestimate the enemy. The French did not believe the Viet Minh would be able to emplace field guns (artillery)in the surrounding hillsides. The terrain was rough and wooded. The Viet Minh did, and all around the French. The French were now in the same position as the US Marines would be nearly 15 years later, at Khe Sanh. The French did NOT have the "B-52" bombers...they surrendered at Dien Bien Phu. The "B-52's" saved the US Marines at Khe Sanh in 1968. Rule number2: NEVER rely on air resupply. Protect your supply line. Air drops aren't reliable and it's hard to maintain adequate tonnage. The British made that mistake with Market-Garden in 1944, and the USMC faced the same issue at Khe Sanh.