Iraq War: How the US military adapted to changing threats
20 March 2013 Last updated at 02:48 GMT
As US forces sped across the desert during the invasion of Iraq 10 years ago this month, many troops were carried in vehicles that lacked armour.
Just a few years later, driving without added protection became unthinkable amid the bloodshed that roadside bombs and improvised explosive devices wrought on US troops and Iraqi civilians.
Throughout the war in Iraq the American military faced an enemy whose ability to adapt tactics and weapons proved increasingly deadly.
The Americans reacted each time by enhancing and upgrading their equipment. But the military forces were often criticised for the slow pace at which they adopted these measures.
Produced by the BBC's David Botti
Additional photos/video: Getty Images, ThinkStock, and the US Army
Sources: Congressional Research Service, Marine Corps Systems Command, US Government Accountability Office, US Marine Infantry Combat Uniforms and Equipment by Kenneth Ewald, Joint Forces Quarterly, US Department of Defense, and period news reports