Thanks for the help all. I finally beat it on hard last night! There were 3 essentials:
-Use direct control with infantry to kill tanks with AT grenades. It is critical to position some infantry with AT grenades in kill spots WELL BEFORE the tanks are even close. The 3 tank killzones I used with my infantry was: the raised platform with cylindrical objects in the north to cover both north approaches, the gate in the east (try to kill right in the gateway to slow future tanks), and the buildings beneath the eastern gate to hit the SE tanks that approach.
-Use ALL the mines (AT and AP). Immediately after game starts set as many people as you can to mining. Mines can be found in boxes in the central ammo warehouse. Put AT mines along the roads north and south of the ammo warehouse. Fill the ammo warehouse with AP mines; it will eventually become a central staging zone for enemy infantry.
-When you get the message that the enemy has given you a break, pull everyone back ASAP! Position fixed guns and tanks at the north/south entrance to the train area. Place some infantry with the fixed guns but place the rest of your infantry in between the ammo warehouse and the buildings on right edge of the train area. There they can pick off infantry coming out of the warehouse and the ones trying to overrun your fixed guns to the north/south.
I made it to the "enemy giving you a break message" using only AT grenades to take out tanks. After that retreated everyone back and slowly lost everyone to subsequent waves. In the end barely had a few squads of riflemen left when it finally hit 100% loaded.
This is by far the most brutally difficult RTS mission I have ever played. I'm still trying to decide if that is a good or bad thing; I think good.
