Just tried this mission again today, and managed to beat it with all secondary objectives complete... and let me tell you, Cobras are key. You'll want every one you can get, even the base model, and you can only afford to loose one or two. You can't hold all both forward flanks, so pick one and concentrate on that and the forward center. You'll still probably loose both flanks, but the side you tried to defend should delay the enemy long enough to keep them from reaching the airbase. For the forward zone you don't defend, pull those units back to the Control Sector closer to the airbase, and reinforce them. Buy up a bunch of recons and spread them around, keeping them out of trouble, and use chopper recon as much as possible. Pull back the recons you start with and redeploy them somewhere safer, because they will die where they are, and almost immediately. The only choppers you'll encounter are scouts, so don't bother with air-defense.
From my experience, the enemy attacks your left flank with lots of armor (T55AMs, T72s), and your right flank with mechanized infantry (in BTR-70s, almost in spamming numbers), supported by some armor. Your center will be attacked by infantry, BMPs, and armor (think... it got so ugly and jumbled up there, I couldn't pick out individual units). You don't actually have to have a command unit in the center in order to complete "Maintain a Forward Position" Secondary objective, just units there in general. Don't bother with expensive armor like the Abrams; they'll just get swamped and picked apart, and you'll want to save them for other missions, I bet. Use cheaper armor instead, like Leo 1A1-1A5s, Chieftains, Starships, Sheridans, whatever. The Bradleys you start with handle themselves well, but they usually all die, so if you want to save them, consider sending in cheaper autocannon units to either bolster them or replace them.
Above all, don't waste your helicopters. If you loose them, you won't be able to respond to enemy attacks fast enough. They are key. Also, keep your units supplied, using your HEMTTs and your Chinook. If your units run out of ammunition, it'll take a long while for supplies or replacement units to get to them, because of the size of the map.