Biden's assertions are based on information from the Department of Defense. In testimony and reports, military officials have said roadside bombs – improvised explosive devices – have caused 70 percent of U.S. casualties.
The Commandant of the Marine Corps, Gen. James Conway, told the Joint Chiefs of Staff in a March 2007 letter the Mine Resistant Ambush Protected vehicle, called MRAPs, "could reduce the casualties in vehicles due to IED attack by as much as 80 percent." Those estimates are based on damages sustained mostly by Humvees, which are commonly used for quick transport but offer little protection from bombs.The trouble with the 80 percent figure is that things are changing rapidly in Iraq. In the past year, military officials have reported that Iraqi insurgents have been using bombs that can pierce the armor of the MRAPs. The stronger bombs have been used in fewer numbers, and it's uncertain how much insurgents will target the new trucks with them, said John Pike, director of globalsecurity.org.