That's a tough one. I think you should ionize all the cars on the train except the ones that don't have guns, this will slow it down enough for you to go on a killing spree for ties, at-sts, barracks, missile turrets, and turbolasers. It's difficult cause they don't give you alot of time, i think only 4 minutes? btw, you CAN destroy the train station that the train goes to when you fail the mission, but it's not really necessary.
Battle is a pure form of expression. It is heart and discipline, reduced to movement and motion. In battle, the words are swept away, giving way to actions-- mercy, sacrifice, anger, fear. These are pure moments of expression.