it took me two tries but this is how I did it.
1. I didn't disembark anyone
2. I saw the little fences on the right and left side of the road, that is where you tell your armored cars to drive through.
3. Move your armored cars/half tracks to the green things and then reverse and move back to the exit. You will see the green things disappear as you tag them.
4. When mounting the little mrs, some barking is in order
5. William Shatner is my hero