Not much is known about the background of the flak troopers, other than that they were Gulag inmates who were forced to carry out their sentences on the battlefield. Because of this, they were given the undesirable task of carrying heavy flak cannons and volatile anti-vehicle mines.
Switches to vehicle mines, that can be placed on vehicles and buildings. When in this mode, if the Flak Trooper is run over, these mines will detonate, damaging the vehicle.
Let's see how this thing works… - Flak trooper, attacking
They are especially formidable when garrisoned in buildings. They are cheap, moderately effective anti-tank units and very effective anti-air units, easily equal to the Javelin soldier and superior to the Tankbuster in terms of versatility. However, they are still very vulnerable to anti-infantry weapons and can be crushed by tanks. Even so, they are an essential complement to any infantry attack force.
When wielding Magnetic Mines and are not selected, Flak Troopers toss the mines like toys, even accidentally drop them to ground, if that occurs, they're seen frightened and expect the mines will explode, thus take evasive action. This is akin to Grenadier squads from Tiberium Wars.
The Hammer and Sickle seen in the Flak Trooper's flak cannon in the cameo cannot be seen in their ingame model.
Flak Troopers status as convicts forced to carry their sentence is based on Shtrafbats - Soviet penal battalions that fought on the Eastern Front in World War II.