U.S. Marine Corps has ordered that it's standard MTV protective vests be made lighter and more flexible. This came after growing complaints from the troops, who have flooded message boards with bad-news stories of how their heavy and restrictive "flak jackets" have put them in danger during combat, A year ago, in an initial response to those complaints, the Marine Corps gave combat commanders the authority to allow their troops to go into action without some, or all, of their protective equipment. The marines tend to be more innovative, and use more initiative, in matters like this. Even so, senior marine officers had been putting off making this decision. That is a form of good news to the junior officers, who actually get shot at, because it meant the brass were finally willing to put their careers on the line, and give the combat commanders the authority to have troops shed armor when the situation calls for it.
Most of the problems came about when marines began receiving a new protective vest, the Scalable Plate Carrier (SPC), in 2007. This one was a little lighter, but a lot less bulky, one (MTV, or Modular Tactical vest) introduced in 2004. First it went to Afghanistan, where moving up and down hills is a lot more strenuous than the generally flat terrain of Iraq. But marines still complained about the 80,000 MTV vests that had been issued, which are considered too heavy and restrictive. Only about 5,000 SPC vests have been issued.
All this is the result of a six year old debate in the infantry community over how much body armor is actually needed. There are times when the troops have to move fast (as when chasing down a sniper). But the senior commanders are under a lot of pressure to keep friendly casualties down, so they tend to insist that the troops wear all their armor all the time. Despite this, some subordinate commanders look the other way when troops shed their armor, or parts of it, to temporarily to get some needed speed. Over the last few years, pressure from the media and politicians has caused several additional items to be added to the standard protective vest. This was welcomed by reservists doing a lot of convoy duty, but not by infantry running around after the enemy. The latest protective vests have a quick release feature, that makes it easier to get the vest off, and back on again.
Many soldiers and marines point out that the SOCOM operators (Special Forces and SEALs) will sometimes go into action without their protective vests. Again, that is done because completion of the mission is more important than covering your ass when a reporter goes after you for "unnecessary casualties."
Many of the troops are willing to take the risk, because they believe, for example, that taking down a sniper when you have the chance, is worth it. If you don't catch the guy, he will be back in action the next day, kill American troops. All this is another example of the fact that "victory" is defined differently, depending on what your rank is.