Fort Deen is a symmetrical map. It has three starting bases for the player and his/her allies on either side of the map. It also has four additional bases, each in close proximity to the starting bases, which are defended by human rebels. In the very center of the map there is an impassable energy barrier, which, when garrisoned by infantry, blocks any direct access by the enemy or the player and his/her allies to the other side of the map. There are however, side-paths on each side of the map that can be used as a secondary route. These paths, however, have an energy barrier that can be activated as well. If all routes to the other side of the map are blocked by energy barriers, there is a teleporter on each players side that can transport the player or the enemy to the other side of the map, beyond the energy barriers, allowing either player to gain quick access to their enemy's side of the map.
Four free base slots are around the center of the map, albeit not in close proximity to each other. Two sniper towers which activate shield doors parallel to the two bases are in the center of the map. Two paths around the outside of the map offer good scout routes, and both contain a forerunner building at their center.
- Fully upgraded Marines or ODSTs can hold out for a long time in the energy wall barricades. Hornets can complement the Marines, hitting the enemy but staying safe behind the barrier.
- Send forces to eliminate a side energy door that enemies have occupied. Have building killers go in a separate direction.
- Putting some units behind the teleporter near the player's base can destroy attackers quickly.
- Aircraft can pass over energy barriers without a problem. This can surprise your opponent when you do a Hawk rush.
- If playing as a UNSC leader, try to send an air unit over and then use Pelicans to transport your attack force over the barrier.
- From a real world perspective, the level is named after Tim Deen, one of Ensemble Studios' senior designers.
- During gameplay, players' Spartans may comment that the planet has 80% the gravity of Earth.