I found this on front page of Wikipedia:
The Battle of Dien Bien Phu was the climactic battle of the First Indochina War between French Union forces and Viet Minh communist revolutionary forces. The battle occurred between March and May 1954, and culminated in a massive French defeat that effectively ended the war. The French undertook to create an air-supplied base at Dien Bien Phu, deep in the hills of Vietnam, in order to cut off Viet Minh supply lines into the neighboring French protectorate of Laos. The Viet Minh, under General Vo Nguyen Giap, surrounded and besieged the French, who were unaware of the Viet Minh's possession of heavy artillery. The Viet Minh occupied the highlands around Dien Bien Phu, and were able to fire down accurately onto French positions. Tenacious fighting on the ground ensued, reminiscent of the trench warfare of World War I. The French repeatedly repulsed Viet Minh assaults on their positions. Supplies and reinforcements were delivered by air, although as the French positions were overrun and the anti-aircraft fire took its toll, fewer and fewer of those supplies reached them. After a two month siege, the garrison was overrun and most French surrendered. Shortly after the battle, the war ended with the 1954 Geneva accords, under which France agreed to withdraw from its former Indochinese colonies.
What many people don’t realize, even some military enthusiasts, is the French made some of the very same mistakes during the 1950s the US military would make during the 1960s and the 1970s in Vietnam. The French and American military both underestimated their opponents. Both the French and Americans assumed military superiority would crush popular support; both were wrong. The Viet Minh victory in 1954 was forgotten or ignored by American military planners; it wasn’t by the Viet Cong. The Viet Cong persistence and knowledge that they had out lasted every single invading force to their lands gave them ability to outlast the American military. High tech weapons and military tactics had limited effect against the very low tech guerilla tactics of the Viet Cong. The argument that it was American policies limited military effectiveness misses the point the Viet Cong exploited those weaknesses. The Viet Cong, like the Viet Minh a decade earlier, ultimately outlasted a superior military force.
The parallel is eerily similar to the war on terror. The United States response to an attack led by a handful of operatives was to launch two full-fledge military operations. The costs of those operations, both in lives lost and money, prevent them from being maintained indefinitely. Terrorists groups understand this. They are limited by not having unlimited funds and operatives, attacks have to be well planned and flawlessly executed to insure maximum effectiveness. One successful terrorist attack will lead to months or even years of response actions costing the victim state millions of dollars. The problem with waging a major military operation against terrorists is violates a tenant of military decision-making. The victory is usually whoever is able to form and execute their decisions before the other guy (getting within their decision making circle). A simple example illustrates this point; think of two fighter jets in combat maneuvering to get on their opponents tail for the kill. If one jet is able to turn more tightly than the other, usually that jet (given equally abilities of the pilots) will win. Decisions made be large, cumbersome bureaucracies can’t outturn those made by a small handful of terrorists focused on single purpose; attack.
As the poet and philosopher George Santayana: "Those who cannot remember the past are condemned to repeat it."