The IED attack against a U.S. Marine Corps Amphibious assault Vehicle last week in Iraq (see image of an AAV from 3/7 Marines in Iraq OIF1)) was a violent illustration of a lesson I learned many years ago in college--back in Warner Schilling's Military Technology class at Columbia University. Every weapon and weapon system usually leads to the development of a counter weapon, and that counter weapon will in turn lead to a counter-counter weapon system--a continual escalation for battlefield superiority. This broad yet simple axiom seems to have stood the test of time, at least up to nuclear weapons, to which no successful counter technology or doctrine has evolved. (Even the civil defense measures during the Cold War seemed to be geared more towards public consumption rather than strategic practicality.)
Last year while in Mosul, I recall seeing photos of a suicide bomber's attempt to blow up a Bradley Infantry Fighting Vehicle during OIF1. The insurgent's body was everywhere and the only damage to the Bradley was a large red stain of blood. Those types of zealous but ineffective bombings are more and more a thing of the past in Iraq. No doubt attacks like those demonstrated to the insurgents that they would have to come up with alternatives to penetrate the armor that the coalition possessed. For awhile at least most of the insurgent IEDs targeted the supply column--vehicles that were not armored or lightly armored and were more likely to be damaged, destroyed, and inflict casualties.
The IED that flipped the Marine AAV, may have diminished the importance of the race to up-armor all the soft skin vehicles operating in Iraq, Humvees and trucks. The Iraqi insurgent's IED capability has escalated to diminish the importance that up-armor may have afforded a humvee or truck eighteen months ago. This isn't to say that up-armor will not help against the casual, crude or misplaced IED, but against the more sophisticated and powerful kinds of bombs increasingly used by insurgents, it will not stave off occasional disaster. The Marine AAV is not the first Infantry Fighting Vehicle to be destroyed by an IED. At least one U.S. Army Bradley infantry fighting vehicle was struck by a "lollipop" IED, with enough force to split it from underneath.