The Great Train Robbery

This mission introduces the diamondback vehicle. You'll want to set up factories to produce many of these quick, laser firing menaces. However, don't neglect your infantry units: continue to train medics, marines, and marauders. They will be useful in completing your main objective and can be left behind to protect your base.

There are also abandoned diamondbacks around the map, and moving any unit near them will add the diamondback to your forces. Even with heavy numbers, it's best to avoid the enemy bases outright. Instead, wait for the Dominion trains to speed towards you and intercept them.

Between assaulting trains, scout the area for resources, diamondbacks, and research opportunities. Gathering bone samples can unlock bonuses after completing the mission, making future endeavors much easier. Don't ignore your base though, as the Dominion will send a squad of marauders to storm your base. Your own combo of marauders and medics will be able to withstand their assault.

With each new train, the Dominion will set up new defense tactics. The first will be direct train escorts, including siege tanks. Destroy the escorts first, and then focus on the train. The next approach will be setting up stationary bunkers. You can either destroy the bunkers before the train arrives, or attack when a train isn't near one. Finally, some trains will have speed boosters, making them only killable from your quick diamondbacks. With all trains eliminated, the mission will end.