The Arm of Orion has overrun New Madrid, one of the most remote colonies of the Empire. The United States Imperial Forces of course can't just stand by and watch and has send an army into the orbit of the planet. Part of this army: the 8th Armored Infantry or 'Section 8' for short. The best of the best the UISF has to offer. Also known as Helldivers, they are able to jump from a spaceship right down onto the planet without any parachute or other help besides their own full-body armor to fulfill mission objectives deep behind enemy lines. The singleplayer-campaign puts the player in the shoes of Alex Corde accompanied by his squadmates to help free New Madrid.

Section 8 is a multiplayer-focused and objective-based first-person-shooter. Killing enemies, capturing control points and completing dynamic combat missions grant victory points that in the end determine the victor of each multiplayer-battle with up to 40 players. Dynamic combat missions come in six types ranging from escorting an Commando as he assaults an enemy base, deploying an outpost at a strategic location or planting a bomb at the enemy base. To complete his job, the player has access to a vast range of weapons including machine guns and sniper rifles, equipment like repair tools and passive modules which increase his shield capacity or weapon damage. The player can change his loadout not only when he's dead but also on the field at deployable supply depots. In addition they also heal him and replenish his ammo.

Supply depots are either created automatically by the game once certain objectives have been met or can be bought and build by players that have earned enough money by killing enemies and completing objectives. Also available on the shopping list are combat structures which include three types of turrets as well as a tank, a mech-like heavy armor and an armored transport. Except for the heavy armor, all vehicles have place for more than one player, especially making the tank a powerful weapon thanks to it's four weapon systems each of which is controlled by a single player.

The armor of Section 8 not only can withstand a drop from high altitudes, it also has an integrated jetpack, allowing for short periods of flight and a booster to temporarily run faster. These functions consume energy which is automatically replenished when not used. The drop from the sky, called Orbital Burn-In, which is the way the players spawn, can be controlled to a limited degree. While the spawn-point can be chosen from a map, the players can decide themselves when to engage the brakes of their suit. While a soft landing allows for the player to immediately go into combat and steer a little bit, it makes him vulnerable during drop-down. A hard landing on the other hand is fast but the player then needs a few seconds to recover from the impact.

While Conquest is the only gameplay-mode available, there are different types of bot-modes available. Besides playing a game without any bot, the host can choose between Balanced (filling the game to the maximum number of players allowed with bots), Coop / Extreme Coop (all players are on one team, bots on the other) and Swarm / Super Swarm (one small team against a large swarm of hostile bots). Only available in singleplayer is the One Man Army-mode which pits the player alone against an entire team of hostile bots.