Very early in the Iraq War, most conventional warfare threats to U.S. military forces were eliminated. Even before "Mission Accomplished" the Iraqi military such as it was, and the disorganized early insurgency lacked tanks, armored personnel carriers, military aircraft, self-propelled artillery, and fixed anti-aircraft artillery. Infantry weapons from personnel with non-military vehicles were the only weapons that remained.
Once these threats were eliminated, one of the main threats to American soldiers was the RPG, the rocket propelled grenade, and other infantry based anti-armor and anti-aircraft weapons of disbanded Iraqi Army units.
This made side armor for American military vehicles in Iraq very important. And, only the heaviest American military vehicles can withstand a solid anti-armor weapon hit. It also made flying in Iraq treacherous and forced U.S. military aircraft to high altitudes.
These threats now appear to be all but gone. For many months, U.S. military casualties have overwhelmingly been caused by road side bombs and rifle fire. Perhaps the odd mortar round is launched. It has been a very long time since I have heard of a U.S. aircraft being shot down by enemy fire, or of a U.S. military vehicle being hit by an anti-armor weapon.
This means that going forward, U.S. military procurement should focus on providing troops in Iraq with vehicles with V-shaped underbodies, designed to resist roadside bombs, which may be only armored otherwise enough to stop rifle rounds and shrapenel, rather than more heavily armored Bradley Infantry Fighting Vehicles and tanks, which devote a great deal of armor (and hence weight, fuel efficency and cost) to opposing tank rounds and anti-armor weapons that the Iraqi insurgents no longer seem to have in great numbers.
Unlike the Hezbollah fighters involved in the Israeli-Lebanon war earlier this year, which involved advanced military weapons that clearly pointed to sponsorship from an anti-Israeli government, the Iraqi insurgents are using a decreasing number of imported manufactured weapons. Instead, they are relying to an increasing extent on home grown weapons to take on the Americans. Moreover, the weapons they are using that they don't make, are increasingly the kinds of weapons available to non-military personnel. This implies either that U.S. weapons smuggling interdiction efforts are working, or that outside governments suspected of involvement, like Syria and Iran, are not shipping weapons to insurgents.
This also adds further credibility to the argument that the insurgency, because it is grassroots based, must be solved with a political solution acceptable to the various and divided people of Iraq. But, it casts doubt on the argument that this conflict is largely the product of outside agitators, and on the regional approach proposed by the Baker Commission.