The most important battlefield innovation is not a weapon
Great aircraft and vehicles aren't very useful without somewhere to park them, and troops need good cover to keep them safe from attacks. So, for all the innovations coming out of DARPA and the weapons being developed by the military, it's the humble Hesco barrier that became an icon of security in Iraq and Afghanistan.
The barriers are a staple of deployed-life where they formed many of the outer perimeters and interior walls for NATO installations.
Originally invented by a former British miner to shore up loose earth in his backyard, the Hesco was first used for military defense in the Gulf War. The basic Hesco design is a wire mesh crate with fabric liner that can be folded flat for storage and transportation. To deploy them, engineers simply open them up and fill them with dirt and rocks. When they want to get fancy about a permanent wall, they can then apply a concrete slurry to the sides and top to seal them.
Even without a slurry added, the walls provided impressive protection. A group of engineers in Afghanistan in 2005 had a limited space to build their wall and so modified the barriers to be thinner. They then tested the modified version against static explosives, RPGs, and 40mm grenades. This thinner version was heavily damaged but still standing at the end of the test. In the video below, go to the 0:45 mark to skip straight to the tests.
Hescos even provide concealment from the enemy while troops are putting them in.
The famous Restrepo Outpost was constructed by soldiers who slipped up to a summit they needed to capture at night and began building fortifications around themselves. They dug shallow trenches for immediate cover and then began to fill Hescos with dirt and rocks for greater protection. When the enemy fired on them to stop construction, some troops would fire back while others would get down and keep pitching rocks into the barriers.
A similar method of construction under fire was used by soldiers in the Battle of Shal Mountain.
Though the original Hesco were great, the company still updates the design. When the military complained that breaking down Hesco walls took too long, the company created a recoverable design with a removable pin that would allow the dirt to fall out. Later, they developed an apparatus that could be attached to a crane to remove multiple units at once.
To rapidly build new perimeter walls like those needed to expand Bagram Airfield as the NATO footprint grew, a trailer was developed that could deploy the barriers in a long line. Each trailer can deploy a barrier wall over 1,000 feet long.
The barriers were so popular with troops that multiple people named animals rescued from Afghanistan after them.