The single player Dawn of War 2 campaign focuses specifically on the Space Marines. Players take the role of a Force Commander caught in struggle spanning three planets, each with varying importance to the Imperium and assaulted by alien forces. The most recognizable factions, Orks and Eldar, appear first, but everyone is soon assailed by a monstrous threat called the Tyranids, which seeks only to consume all life on the planets. Soon, players will be trekking back-and-forth between worlds, fighting numerous battles across their territories, and picking up new skills and wargear in doing so.

Gameplay focuses almost completely on tactical combat. There's no base building involved, nor is there a chance to assemble huge armies to bring the Emperor's might down on his foes, so players who appreciated those aspects of the previous games will be disappointed. More upsetting is the fact that there aren't any super units to build like the Ork Squiggoth or Eldar Avatar (although players will battle against some of them). There aren't even any vehicles in single player. Fortunately, Commander powers like calling in orbital bombardments still exist, although in a limited fashion.

Players drop into each mission with a small handful of squads (a maximum of four) and must survive with what they have. Each squad is represented by a hero character and serve specific functions. For example, Cyrus and his scouts can go into stealth mode to move ahead of the group, act as spotters, or use a high powered sniper shot to take out priority targets. There are six different squad types in total, but only four can embark on a mission at once. At early stages, players will have to make frequent use of the environment as cover to help reduce damage. Most of the environment can be destroyed, so cover usually doesn't last very long, but it's fun to watch walls crumble under the might of heavy gunfire or giant explosions. Completing missions earns XP, and new levels bring skill points that can be distributed across four attributes to unlock special abilities. Wargear can also be collected as battlefield drops from slain enemies or as rewards for completing tasks. However, even though players can exchange unwanted items for XP, there's no way to purchase anything, so outfitting heroes leaves much up to chance.

Apart from the story-based missions, confrontations fall into one of two categories. The first are "Seek & Destroy" types, where players plow their way across the map and confront a single boss creature at the end. Along the way, players have the option of capturing strategic assets like shrines and foundries, which help get the most use out of certain powers. Once those assets are secured, players spend most of the game defending them. These missions usually involve fortifying a position and holding ground against waves of oncoming hordes, finished by a boss creature that comes in to stomp on some Space Marines. Distress signals periodically pop up across the three worlds, and some of them have turn limits for answering them. Missing a deadline means losing an asset and the benefits it brings. Players aren't expected to answer all the distress calls, but they'll have to decide which ones take priority. Completing missions with extra style, such as exterminating all foes, having no squads leaders knocked out, and doing it all at great speed earns bonuses toward additional drops in the same day, getting more done in a single turn. Search & Destroy type missions usually take an average of 20 minutes to finish, if players take their time purging the territory or alien incursion. Defensive missions normally don't last more than 10 minutes, making Dawn of War 2 a very fast (albeit a slightly redundant) game to play. These side quests can become pretty stale after a while, especially at high levels, when our heroes became so powerful that no force could stand against us. On the downside, there's no way to save a game mid mission, nor is there a way to revert to a previously saved game. That means all decisions regarding skill points and winning or losing strategic assets are permanent.