Asymmetric warfare is a phrase used to describe a situation where a militarily weaker side can exert leverage on a militarily stronger side far beyond the power of its weapons.
It is a concept that some western governments have been forced to learn the hard way in recent years.
The conflict in Afghanistan could be said to follow this model, as can the American war in Vietnam.
A book out this month entitled 'War Without Fronts: the USA in Vietnam' is the first to reveal that atrocities and war crimes against civilians, such as the My Lai massacre, were more the norm than the exception in the Vietnam war.
The BBC's Dan Damon discussed the parallels drawn between the two conflicts with journalist and war historian Max Hastings and the author of the book Professor Bernd Greiner.
First broadcast 17 August 2009