The new, heavier, body armor arriving in Iraq is creating a potential public relations problem. Many of the troops don't want to wear the new stuff. Why? Because the heavier new armor could get them killed. The new protective vests includes side armor.
Side armor, which adds about ten pounds to the 16 pound weight of the Interceptor Protective Vest, has been available since 2003 (when 250 sets were sent to Iraq.) About a thousand sets were delivered in 2004, and more last year. Side armor is obviously not new, but its availability has not been widespread. While the side armor provided useful protection, the added weight (for a trooper already carrying over fifty pounds), and material, restricts movement. The new armor is most popular with those guarding convoys. These troops spend most of their time sitting down, and the side armor provides additional protection from roadside bombs, which throw out a lot of fragments, at troops sitting facing forward. The bombs are often accompanied by an ambush force armed with machine-guns and assault rifles. Sometimes, the troops have to get out of their vehicles and battle the ambushers. This is often intense and disorganized combat, with fire coming from all directions. Again, the side armor can be very useful. But the troops won't be running around so long that the additional weight and movement restriction will become a major problem. For the same reason, combat troops that are spending most of their time in their vehicles, don't mind the disadvantages of the side armor. But infantry that are out running around most of the time, going up stairs, through windows and battling the enemy in an urban environment, nimbleness is more important. Some of these guys have been known to leave the back plate, or even the front plate, out, just to save a few pounds. Not being able to scramble through a window in time can get you killed, as can many battlefield maneuvers that put a premium on speed and maneuverability. American commandoes, including Special Forces, often go into action without the body armor, because the consider mobility more important.
These different attitudes towards how much armor to wear are similar to those found in police forces. That's why the police have both lightweight armor (worn by most cops, most of the time) and heavier rigs for SWAT teams or anyone out on a raid, and even heavier getup for bomb disposal personnel.
The senior commanders are under a lot of pressure to "protect the troops." Many people back home have invested a lot of themselves in efforts to get better armor for the troops. Hearing that the troops value lightness and speed, over armor and more weight, will upset some politicians and pundits. But if the opinions of the troops counts for anything, weight matters, often more than anything else.