How do you complete the Surprise Attack and Pain Train challenges?

Question

How do you complete the following challenges:

Meet the Dwarves - Surprise Attack

Meet the Tribe - Pain Train

Answer 1

The solution for Pain Train is:

First and Second Move - Use a Meat on the Witch and then attack the Gunner

Third Move - Explode the Gunner's corpse with the Witch, which will take out the two units beside him.

Fourth Move - Use a Typhoon to move the Engineer closer to the Witch.

Fifth Move - Use the Witch to attack the Engineer.

Answer 2

Surprise Attack is pretty simple, if you know about the ability of the Grenadier to attack over enemy units. Move one of the Engineers onto an Assault Boost square, then spawn the Grenadier, move him to the Attack Boost square and then hit the crystal twice. Alternatively, you can move both Engineers to both Assault Boost squares and then only attack a single time with the Grenadier.