Working conditions for the infantry have changed considerably in the past two decades. The biggest change is the equipment that must be carried. Until the 1980s, you could strip down (for actual fighting) to your helmet, weapon (assault rifle and knife), ammo (hanging from webbing on your chest, along with grenades), canteen and first aid kit (on your belt) and your combat uniform. Total load was 13-14 kg (about 30 pounds). You could move freely, and quickly, like this, and you quickly found that speed and agility was a lifesaver in combat. But now the minimum load carried is twice as much (27 kg), and, worse yet, more restrictive.
Over the last seven years, this has translated into some dramatic changes in training. In Iraq, troops found they were not in the best condition to run around with all that weight. Plus, the vest constricted movement, and that took time to adjust to. Commanders complained about troops not being properly trained, and that led to a series of changes in basic and unit training. The big change in basic was to condition troops to handle the heavy weights they would be carrying, for extended periods of time. This was particularly critical for non-combat troops (especially those operating convoys) outside of camps (where you usually didn't have to wear armor and combat gear.) New exercises were developed. Infantry troops got several months of additional training after basic, and had plenty of opportunity to adjust to moving around wearing 14 kg or more of gear.
The officers who ran basic training got a lot more feedback from the front, about things recruits needed to know. So more emphasis was placed on brawling (for subduing captives), clearing rooms, new first aid techniques and using GPS and other electronics found in military vehicles. Old items, which surveys found were rarely used, were dropped from basic.
This all began when more essential equipment was added in the late 1980s and early 1990s. The biggest, and heaviest, problem is body armor. Although the new armor offered better protection, it was heavier and bulkier, thus inducing fatigue and hindering mobility. This often led to battlefield situations where a less tired, and more agile, infantryman could have avoided injury. Military and political leaders usually do not appreciate this angle. But the troops do, as it is a matter of life and death for them.
Currently, the lightest load carried, the "fighting load" for situations where the troops were sneaking up on the enemy and might be involved in hand-to-hand combat, is 28.6 kg (63 pounds). The "approach march load," for when infantry were moving up to a position where they would shed some weight to achieve their "fighting load", is 46 kg (101 pounds). The heaviest load, 60 kg (132 pounds), was the emergency approach march load, where troops had to move through terrain too difficult for vehicles. As in the past, the troops often ignored the rules and regulations and dumped gear so they could move, or keep moving.
In Afghanistan, the problem is made worse by the high altitudes (up to 5,000 meters) the troops often operate at. The researchers found that in Afghanistan, even though the infantry were in excellent physical shape, troops would sweat nearly 59 cl (20 ounces) of fluid an hour while marching at high altitudes in bright sunlight in moderate temperatures. That meant more weight, in water, had to be found to keep these guys going.
While troops complained about the new protective vests, they valued it in combat. The current generation of vests will stop rifle bullets, a first in the history of warfare. And this was after nearly a century of trying to develop protective vests that were worth the hassle of wearing.
It wasn't until the 1980s that it was possible to make truly bullet proof vests using metallic inserts. But the inserts were heavy and so were the vests (about 25 pounds). Great for SWAT teams, but not much use for the infantry. But in the 1990s, additional research produced lighter, bullet proof, ceramic materials. By 1999 the U.S. Army began distributing a 16 pound "Interceptor" vest that provided fragment and bullet protection. This, plus the 3.3 pound Kevlar helmet (available since the 1980s), gives the infantry the best combination of protection and mobility. And just in time. Since the end of the Cold War, more of the situations U.S. infantry find themselves in involve lightly armed irregulars who rely more on bullets than bombs. The bullet proof vest eliminates most of the damage done by the 30 percent of wounds that occur in the trunk (of which about 40 percent tend to be fatal without a vest). The Kevlar helmet is also virtually bulletproof, but it doesn't cover all of the head (the face and part of the neck is still exposed). Even so, the reduction in deaths is significant. Some 15-20 percent of all wounds are in the head, and about 45 percent of them are fatal without a helmet. The Kevlar helmet reduces the deaths by at least half, and reduces many wounds to the status of bumps, sprains and headaches. Half the wounds occur in the arms and legs, but only 5-10 percent of these are fatal and that won't change any time soon. Thus since Vietnam, improved body armor has reduced casualties by more than half. The protective vests used in Vietnam and late in the Korean war reduced casualties by about 25 percent since World War II, so the risk of getting killed or wounded has been cut in half since World War II because of improved body armor. Much better medical care (especially rapid evacuation of casualties by helicopter) has helped change the ratio of dead to wounded from 3:1 during World War II to 5:1 today.
The Interceptor vest was an improvement in other ways. It was easier to wear, and was cooler in hot climates because you could more easily adjust it to let some air circulate. You could also hang gear from the vest, making it more a piece of clothing. It's still hot to wear the vest in hot weather, but if you're expecting a firefight, it's easier to make the decision to wear the vest. You know it will stop bullets. U.S. troops who have fought in Afghanistan, and hit with rifle bullets that would have penetrated earlier vests, are already spreading the word throughout the ground combat community. All you have to do is exercise in such a way that you are better able to carry the weight, and still be mobile.