Defensive missions and objectives?

[functional]

Hey guys. I don't have any idea how to succeed in such missions and objectives where you have to defend. I'm not sure why.

Good example is the Soviet mission, The Last Stand. How can I succeed here?

My AT guns get destroyed in seconds because they miss the tanks and tanks hit them. My infantry will get killed completely by their tanks and soon their infantry is swarming all over the trenches, killing even the last AT guns I may have, if any.

And yes, I know, the mission is not to hold the whole attack with first line, but it gets destroyed already at 2 ships left. And I even try to buy heavy squad, but it's useless. The AT rifles are useless vs their tanks, they can't even stop the tracks to be honest.

They just get too soon to second line and I have layed zero mines there.

This also applies to second mission of Soviet Campaign, my friend did it for me.

Also, it may just be, that it's because I don't give the infantry any extra ammo. Do they just run out quick out of ammo and so the defenses get breached by infantry that killed my men, instead of their tanks?

Some tips would be really appreciated :]