In Defense of Loyalty

A standard combat mission as the Space Marines, you need to destroy the enemy Eldar fortifications after an initial defensive scramble.

Mission Prep

You are forced to only have Gabriel Angelos and Kill Team Ironmaw Squad as your Elites, but you can choose all three Doctrines.

• For your first, pick Ablative Armor - Land Speeder. You'll see why soon
• For your second, pick Blessing of the Omnissiah to make your buildings and Listening Posts give a healing aura to Vehicles, such as the Land Speeders
• For your third it does not matter as much. Thunderhawk Re-Deployment is an option if you are considering trying the Whirlwind and want to improve its mobility, but Tip of the Spear to allow Listening Posts to reinforce and Improved Scope to improve Devastator ranges in cover are also viable options.

Mission Strategy, Hard Mode

1. You will initially warp into a zone with the Eldar fighting Imperial Guard. Destroy the attacking force, and also build a couple of Devastator Squads to help defend against the next couple of attack waves.
2. As part of the defense you also have to push forward a bit to rescue Jonah Orion before he dies. This is not too difficult, Gabriel with Kill Team Ironmaw should be able to provide enough backup to Jonah with the troops he has available.
3. Once Jonah is rescued and joins you is when the main standard push begins. You have immediate access to two PoCs with a number of nodes, also paired with nearby Heavy Cover shields. Start by building and placing at least a couple of Devastator squads in each Heavy Cover and you will be in a good initial defensive position, especially if you picked the Improved Scope doctrine earlier. The enemy will periodically send infantry attacks at you, from the two main directions, but a pair of Devastator squads in each Heavy Cover dome will make very short work of them especially if you start upgrading their damage.
4. Now it is time to see what Landspeeders can do; build a Machine Cult, but you don't necessarily need to build through them; you can also build through the Drop Pods. Also make sure to upgrade your income at your two PoCs, and upgrade your Stronghold tier. NOTE, you cannot avoid the income drop from built units if you build them in the Drop Pods, the income drop happens the instant the unit has finished construction but before they are deployed.
5. You will see as a secondary objective the need to rescue various troops around the map, but the units in question do not actually start to take damage until you first reveal them. So before you venture out anywhere you can just park yourself at the base building up a good Landspeeder force and upgrading tech. Once you have 5 landspeeders with Multi Meltas and all of the Vehicle health and damage upgrades, you can set out.
6. With all of the Landspeeders at once, just attack-move at the various locations. Eldar do not have good anti-vehicle weapons so many of the units, like Banshees and Dire Avengers, will do nearly no damage to your Landspeeders. The few times you encounter enemies that can do a bit more damage like Dire Avengers or Shadow Spectres, just command your Landspeeders to attack them directly and they will die VERY quickly given the Speeder's excellent anti infantry weaponry.
7. Feel free to explore widely, the Speeders have the mobility and there are quite a number of Resource Drops all around the map. You should find more than enough to build at least two more Landspeeders and do it through the Drop Pods; once they're done you can land them right next to your main Speeder force no matter where they are, instead of having to fly them all the way from your main base to the front lines.
8. Watch the health of your Speeders; there are Health pickups scattered around the map and one of them will fully heal a Speeder, but if need be fly them back to one of your Listening Posts (where hopefully you've also placed a Servitor or two) to repair them quickly, then send them back out.
9. Keep hitting the bases, a medium squad of Landspeeders fully upgraded with Meltas will tear through everything in sight quickly, until you have rescued the 4 squads and destroyed the two main bases (rescue the squads first).
10. Once the 2 main bases are defeated and the main Power Core is revealed, just push forward as you have been to get to it and destroy it. There are a couple of Dawn of War III/Wraithblade squads spread out that are a little more dangerous to your Landspeeders; they will be defeated in a long fight but they can usually get at least one salvo of shots out, which can do notable damage to a Speeder. But you still shouldn't have difficulty dropping at least one of the Squads then go straight for the Power Core; even if you lose a Speeder or two you should be able to quickly destroy the Core, and you win the mission as soon as the Power Core is destroyed.