Supreme Commander is set in the distant future, and humanity has split into three competing factions. The United Earth Federation represents order and empire, the cybernetic Cybran fight for independence, while the alien-enlightened Aeon seek to liberate the universe. The single-player campaign is divided into three smaller campaigns, letting you battle from the perspective of each of the factions. Unlike those in most other RTS games, where all three campaigns would usually be tied together in a linear fashion to tell a bigger story, the campaigns in Supreme Commander all stand alone. Each faction fights for what it believes in, and hence, no side is really "evil." It’s a nice touch, because that mentality captures the essence of war.

The game’s biggest asset is its sheer size, which is measured in virtual kilometers. Though you can battle it out on "small" maps that are a mere 5km-by-5km, the average maps are 20km-by-20km large, and the largest maps weigh in at a whopping 81km-by-81km. And while the units you command are a bit oversized, this still translates into giant battlefields that give you plenty of room to maneuver. You no longer have to worry about a single chokepoint like you do in most RTS games. Instead, you have the freedom to experiment more. This also means that you need to be wary of enemy attempts to slip around your defensive points. But that’s the nature of war. The entire sense of scale is exciting because you can finally experiment with tactics. Meanwhile, real-world concepts such as reconnaissance become even more important. Thankfully, Supreme Commander makes such tasks easy with the ability to queue up commands for all sorts of units. Scout planes can be ordered to patrol the periphery of the maps, engineers can be given build commands to keep them busy for a long time, and armies can be sent on a zigzag path deep into enemy territory, all with a few clicks.

Often during the campaign, you’ll achieve a set of objectives only to watch the map then double in size, and then double again after you’ve achieved the next set of objectives. Each time the map grows, it unlocks more room to maneuver and more strategy. Size translates into open-ended depth in this game. For instance, assume you’re battling a heavily entrenched foe. How you take the opponent down is up to you. You can try raids to cripple the other side’s economy by destroying mass or energy facilities. You might find a weak spot in the defenses and send bombers through it, then target antiaircraft positions to open the way for further air assaults. If you’re building nuclear missiles, you might build artillery positions to take out any strategic missile defenses, and once those are out, unleash nuclear missiles. You can pretty much open up the entire playbook and experiment with different tactics and different combinations of units. And these tactics apply to all of the factions equally, because aside from visual appearance, factions basically mirror each other. This equates to a general lack of personality to each faction, as well as to the game as a whole, which is disappointing because each of the factions has an interesting backstory.

You can try and overwhelm your enemy with sheer numbers, build fewer numbers of high-quality units, or do a mix of the two, with cannon fodder to draw fire away from the heavy hitters. There are three "tech levels" that feature different units, buildings, and vehicles, and at the lowest level you’ll have basic units such as light and medium tanks, fighter interceptors, submarines, and bombers. At higher levels, you’ll gain access to naval destroyers that can sprout legs and walk on land, siege assault bots, ballistic-missile submarines, and much more. Your engineers can also build gigantic artillery pieces that hurl shells across the map to soften up enemy defenses.

In most real-time strategy games, the act of building a factory on the battlefield is an act of utter contrivance, though in the fiction of Supreme Commander, it makes sense. As the game is set thousands of years in the future, humanity has figured out how to transform matter and energy in a way that’s similar to the replicators on Star Trek. That means that a single Supreme Commander can take the raw materials of a planet and quickly build factories that churn out war machines. It also simplifies the resource system to the most rudimentary concepts. In Supreme Commander, there is only energy and mass. Both are critical to building a strong economy to churn out hundreds of units. While energy can be obtained through various generators and power plants, mass is restricted to a handful of points on the map where you can build mass extractors that mine the planet’s core. The geographic distribution of these mass-extraction points will result in desperate battles to capture and hold large amounts of territory.