From Popular Mechanics:

The Overloaded Soldier: Why U.S. Infantry Now Carry More Weight Than Ever
Technology was supposed to be the solution. Instead, it added to the problem.

By David Hambling, Dec 26, 2018

…even official documents describe carrying a 100 lbs. as standard. In the ensuing debate about whether this was realistic, one marine infantryman described carrying more than 200 lbs. during missions in Afghanistan.

The why of the weight starts with body armor. Standard Interceptor body armor plus helmet weighs more than 20 lbs., and the total rises if additional elements are added to protect the neck, arms, groin, and shoulders. “The lesson in operations in the Middle East has been that body armor saves lives, so the default is to put it all on,” says Jack Watling of UK defense think tank RUSI. Watling was embedded in Iraq and has direct experience of operations in several other theaters.

A M4 carbine and ammunition add another 15 lbs. or so. Then there are grenades, food, and water, a poncho, and liner, plus personal items such as a flashlight, night vision gear, and medical kit. This personal equipment along can easily run to 70 lbs.

We haven’t even mentioned squad and platoon weapons, and let’s face it: Someone has to carry the ammunition. A single 60mm mortar round weighs four .lbs, as does a rocket for the AT-4 launcher. A belt of ammunition for the squad’s M249 machine gun weighs six lbs, and soldiers tend to carry all they can. “There’s direct correlation between how much fire you can put down and who wins,” says Watling. “The requirement for ammunition is not going to go down.”

And then there is the bane of every technology user: batteries. “Almost everything a soldier carries today requires batteries,” notes James King in a piece for the Modern War Institute. Batteries for the platoon’s AN/PRC-117 radio weigh four lbs. each, and the radio burns through them rapidly. King estimates that the average soldier goes into action with a hefty 20 lbs of batteries.

With its weight problem seemingly multiplying, the military is trying to find lighter solutions. The Pentagon already makes everything from Kevlar, carbon fiber, and other lightweight materials, though this trend has led to a widespread joke: A soldier carries 100 lbs. of the lightest kit imaginable.