The U.S. occupation of Iraq is over. The Afghanistan war is winding down. Today America faces “emerging threats in an increasingly sophisticated technological environment,” according to Gen. John Campbell, the Army vice chief of staff.

For the U.S. ground combat branches that means a renewed emphasis on fast-moving armored warfare. The Army and Marines are dusting off heavy vehicles that played a minor role in Iraq and Afghanistan.

In this series, we spotlight some of the more obscure, and fearsome, armored behemoths. The battle wagons of a new era of warfare. The focus of this volume—the Army’s very troubled Mobile Gun System.

In the 1990s, the U.S. Army realized it had a problem. The solution to that problem was, in part, a wheeled armored vehicle that almost everyone seems to hate—and which is quietly fading away after just a few years in frontline service.

The Stryker Mobile Gun System has a tumultuous history. In the years after Desert Storm, the Army concluded that its light airborne forces were quick-reacting, but lacked firepower.

By contrast, armored and mechanized units—with their heavy tanks and fighting vehicles—possessed the firepower the paratroopers lacked. But owing to their sheer mass and complexity, the heavy units could take weeks to deploy to a war zone.

The Army wanted forces that combined some of the airborne troops’ nimbleness with elements of the armored forces’ fighting strength. The result is the Stryker brigade, a relatively new kind of formation riding in eight-wheeled medium armored vehicles.

The General Dynamics-built Stryker weighs just 20 tons, compared to 70 tons for an M-1 tank. But the reduced weight comes at a cost. The $5-million-apiece Strykers have thinner armor and smaller weapons than a tank. The most heavily-armed Stryker is the Mobile Gun System with its 105-millimeter cannon. An M-1 packs a 120-millimeter main gun.

The Mobile Gun System is, in essence, a medium tank—albeit with wheels instead of tracks.

The Stryker MGS, like the whole Stryker concept, is a compromise between competing demands. All the Stryker vehicles—there are many variants—have their critics. The Israeli army evaluated the Stryker and declared it a “piece of junk.” But the MGS is easily the most controversial … and least-loved.

The first gun-Strykers deployed to Iraq in 2008. Soldiers loved the vehicles’ ability to fire shotgun-like canister rounds, “shredding a path 75 meters wide out to 300 meters,” according to Army Times.

But the MGS design crams a lot of equipment into a small space, and as a result it’s crowded for its three-person crew. The hatches are too small for crew members to quickly escape in the event of a fire. And the overstuffed MGS lacks air conditioning. In Iraq, the 150-degree heat forced the Army to quickly outfit gun-Stryker operators with special cooling vests.

Moreover, the main gun fits inside a pod that rests atop the Stryker’s hull. To save weight, the pod is unarmored. “The gun pod can be easily disabled,” the military’s testing agency reported. No MGS can expect to last long in a sustained firefight against a determined foe.

The Stryker MGS was never meant to be a tank like the M-1—but it could find itself doing battle with enemy tanks. “The primary weapon systems are designed to be effective against a range of threats up to T-62 tanks,” the test agency claimed. The Russian T-62 dates to the 1960s.

Going up against more modern tanks—T-72s and later—the MGS would probably lose. Like the Marine Corps’ failed Expeditionary Fighting Vehicle, the gun-Stryker occupies a middle ground between contradictory requirements—basically, weight versus firepower. As a consequence, it’s not particularly good at anything.