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Against Eldar you need to ensure that you hit
first, and that you dictate the engagements. Eldar armies frequently have several formations offboard in reserve, arriving via webway or air assault. An Eldar deployment zone is typically thinly defended in turn 1 - you can use that to get in and cripple a large part of the enemy army before it starts to activate.
Here's a possible Alpha Strike list, with annotations:
Alpha Strike , 3000 POINTS
Codex Astartes (NetEA Army Compendium v20120208)
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TACTICAL DETACHMENT [375]
6 Tacticals, Supreme Commander, Rhinos
Stays as mobile reserve, to guard Blitz and to ensure the SC (with his reroll) is on table from startTACTICAL DETACHMENT [375]
6 Tacticals, Drop Pods, 2 Dreadnought
Follows a bombardment down. If possible, position to support the T'hawk assault, then consolidate the devastators such that the devastators can support the tacticals in a follow-up assault. This is a favorite Eldar tactic, also, and Eldar have a much easier time of time due to Hit'n'Run. However, if the enemy is still deployed close together in the deployment zone, it can be executed by Marines as well.TERMINATOR DETACHMENT [400]
4 Terminators, Chaplain
Teleport in to clear the way for the THawk assault. If the enemy carelessly left a guardian host exposed, they can also take on those, if they hit them from the soft side.LAND SPEEDERS [200]
5 Landspeeder
LAND SPEEDERS [200]
5 Landspeeder
Excellent to set up support in preparation for engagements.THUNDERHAWK [200]
Planetfall if the opponent has heavy AA. Otherwise, use a normal air assault to set the devastators up just right to eradicate one or more enemy formations.DEVASTATOR DETACHMENT [300]
4 Devastators, Librarian
DEVASTATOR DETACHMENT [300]
4 Devastators, Librarian
8 Devs + Librarians puts out enough firepower to wipe most eldar formations (if not in pure FF, then in combat res). Use after any scout screens are cleared to kill a high-priority target - eg a Storm Serpent, or a guardian host.STRIKE CRUISER [200]
Provides an initial bombardment, allows drop pods, and allows the thunderhawk to planetfall in.WARHOUND TITAN [275]
All-round great unit that provide mobility and good MW shooting.THUNDERBOLT FIGHTERS [175]
2 Thunderbolts
AA, and to chase broken formationsA successful (and lucky - Alpha strikes always rely on good fortune) Alpha strike would see a turn 1 bombardment and drop pod deployment, followed by a retain and a terminator assault, which should break one formation. The second activation would then see a T'Hawk depositing 8 devastators, who (with support from tacs and/or terminators) eliminate an enemy formation. A retain & engage with the tacticals, with support from devs and/or terminators should then see a third formation broken or destroyed. At this point, you have about a third of your army in the middle of the smoking remains of his deployment zone, threatening his blitz, and having crippled at least part of his strategy. Extra bonus points for trapping enemy formations in the webway, if he carelessly relied on the Storm Serpent to survive... Retaliation from Revenants can be expected to be bloody, but should ultimately be survivable for Marines. In turn 2, try to catch them in crossfires (speeders are useful, here), the Holofields is a lot less scary then.