I agree with both of the other solutions, utterly brilliant! by following these you should beat each hardcore war in 13-16 turns easily!
Where battle is concerned i always use this for battle space deployment:
(if you are doing battle early on you may not have such a large deployement to start with, so just be smart, use 1 of each type to begin with, maybe forgetting about the tanks as you have engineers and artillery etc)
1: Command Vehicle
3: Tank (this always did the least work so feel free to swap out)
4: 2x Artillery (absolutely essential)
5: 3x Engineers (in cover on your front line)
6: 2x Choppers (use these to sniff out hostile artillery and find targets for your artillery)
Check out this map of the strategic layout, it will help you understand what im trying to explain (its hard to explain non visually)
Always position artillery at the rear of your force, try and put some distance between to two units, imagine a line between them being parrallel to the enemy, the green line in the picture represents the firing solution of the artillery, as you can see you are covered from all angles. However, you can not see right to the edge of the firing solution unless you have attack upgrade 4 on artillery, so this is where your choppers come in, just fly around and then when you get a visual have the artillery pound them!
Your engineers are the ONLY thing that will keep hostile chopper unit away, the apc is quick at taking sheilds down but your engineers will always have them running away without even firing, what you will find is that the choppers will keep going back and forth and every time they will loose a little health.
For paris (which the picture is based on) i took two uplinks that were within my forces area, you really only need one, but have two if you have the ability to airstrike as you will want air strike and electronic warfare upgrades on these.
Use your choppers as scout vehicles (example is the blue lines in the map picture) and as emergency firepower if you find a tank encroaching on your position (again your engineers will more than likely scare these off!) if you do find your unit taking artillery fire scout around quick with your choppers, try not to engage directly as a hardcore AI is the master at getting the upper hand (you will soon find APC's on your ass!) insead use EMP followed by airstrike as emp lower sheilds and stopd them from firing.
What you will find is that nearly all battles and seiges will be full of choppers, infantry and transports (APC's) this method works on every map type i have played and thus far in 48 hours from start to finish i have managed the JSF and RUSSIAN hardcore wins both in less than 16 turns (about 4hours each)
As i said before you dont really need a tank at all, but it just feels more complete having it there, sometime did swap it out for another chopper or Transport (APC) depending on how heavy the opposision was.
Remember to keep some distance between your units, on the map above this is fine apart from the centre point where your tank, apc and an engineer squad are, the AI will never use a nuke etc on your unless he can take out 2+ units at once, sometimes you just have to bite it but you will never loose more than 2-3 units in a nuke using this method, and these should be your first losses meaning you are left with the enemy out of reserves with only 5 or left units left on the battlefield whilst you have 7 on the battlefield and around 7 in reserve. He will crash an up link, but you have two so it doesnt matter... and if he did use the super-power, you have that bad boy to play with ;-)
Thanks again to the other solutions that allowed me to get as far as i have, conquest is a doddle! check them out!!