1. Space Marines units are, generally, the most durable in the game. They donít (aside from a few exceptions) have shields like Eldar units and they arenít as numerous as Orks. They are extremely effective at prolonged encounters, but are less effective at short and against hit & run tactics.
2. Unlike the remaining factions, they arenít limited to recruiting units at the base buildings. This faction can use Orbital Relays to send drop pods on the battlefield. Thanks to them, you can recruit a unit, prepare it and then drop it almost anywhere on the battlefield, allowing it to join the fight immediately and surprise the enemy.
3. It doesnít mean that you shouldnít recruit your units at buildings. Quite the opposite Ė you should use ďnormalĒ recruitment method in most cases, reserving the possibility to use an Orbital Relay to drop a unit on the battlefield when itís actually required to do so. Remember Ė Orbital Relays take long time to become active again.
4. Remember that upon landing, Drop Pod sent from the Orbital Relay will deal damage to the enemy units it hits. The damage isnít high, but the enemy units are also knocked away once the pod lands on the ground, allowing you to create some confusion in the enemy ranks.
5. Drop from an Orbital Relay takes several seconds from the moment you set up the beacon and location. Normally, the enemy wonít be able to see where youíre going to drop the pod and that youíre planning to do so, as the marker is visible to the player and his allies only. However, if there are a Detector unit in the area, the your foes will be able to see the beacon and prepare accordingly.
6. Aside from units, Space Marines can also drop a defensive Drop Pod with the Orbital Relay, one called Deathstorm. Itís a heavily-armored pod that, once on the land, opens, revealing 5 heavy cannons inside. After a brief delay, Deathstorm will start firing at the nearby enemies, dealing huge damage. Proper placement, especially on the back of the enemy group, where, normally, there are sniper and long-ranged and vulnerable units, can devastate the enemy army, taking out multiple squads before the enemy even reacts. Deathstorm disappears after several seconds have passed or if the enemy is able to destroy it. You canít move it once it lands on the battlefield.
7. Space Marines can call down a special standard on the battlefield, with the ability Plant the Standard. Once used, a standard will appear on the specified location, knocking away enemies in the landing area. Afterwards, it sets up, offering powerful bonuses to allied units in the area. The effectiveness of the standard increases as your tech level goes up, offering more powerful bonuses and even allowing your units to heal when in the range of it. Be wary though, as the enemy can capture the standard by placing any unit near it, disabling all the benefits it offers.
8. Orbital Bombardment is the Super Ability of the Space Marines. With it, the player can set up a special beacon, which, after specifying the target area, begins the orbital bombardment. All of the enemy units in the area are levitated, receiving damage at the same time. As the orbital bombardment continues, the damage it deals increases significantly. This ability can devastate the entire enemy army, especially if you can set it up on the back of the enemy army. However, keep in mind that the enemy can capture the beacon by placing any unit near it. Once it happens, the orbital bombardment will continue, but you wonít be able to control the beam and it wonít levitate units anymore.
9. Remember to select your elite units with care. Gabriel Angelos is a good choice for the early game, as he is capable of defeating multiple squads on his own and he remains effective during the whole game. Additionally, he mitigates the lesser melee effectiveness (in comparison to other factions) of Space Marines units Ė other factions have more units for the task (the Dreadnought is the exception, but this unit is quite expensive and you wonít have access to it during the first 15+ minutes).
10. Space Marines are the faction that is the most novice-friendly of all the ones available in the game, especially to hose players that never played Dawn of War games before. Their armies consist of infantry units and machines, making them the easiest for players to find themselves in. This is the reason why you should choose this faction if you arenít familiar with the franchise, to learn the basics of the gameplay.