Much of western military thinking has traditionally assumed that conflicts will involve conventional warfare against an opponent of comparable might, using similar weapons on a known battlefield.
However, military experts have been pointing out for years that resistance forces in places like Chechnya have been conducting a very different kind of war, in which defenders fight on their own terms, not those of the enemy — petrol bombs against tanks, for example. This has been given the name of asymmetrical warfare by counter-terrorism experts, a term that appears to date from the early 1990s. In it, a relatively small and lightly equipped force attacks points of weakness in an otherwise stronger opponent by unorthodox means. All guerrilla activity, especially urban terrorism, falls within this definition.
The attacks on the US on 11 September are a textbook example and the term has had wide coverage since. Some writers extend the idea to any military situation in which a technically weaker opponent is able to gain an advantage through relatively simple means. An obvious example is the landmine — cheap and easy to distribute, but difficult to counter. Another example sometimes given is anti-satellite attacks, in which it is much easier and cheaper to knock out space-based weapons than to put them in place to start with.
Welcome to the world of asymmetrical warfare, a place high on the anxiety list of military planners. In the asymmetrical realm, military experts say, a small band of commandos might devastate the United States and leave no clue about who ordered the attack.
New York Times, Feb. 2001
In this asymmetrical warfare, the weak terrorist attacker has the advantages of selectivity and surprise; the powerful defender must strive to prevent attacks on many fronts.
Newsday, Sep. 2001