Hi Ketch,
When done right, and with a little luck, a few AFVs to the enemy rear can be very rewarding and a lot of fun. Of course, you shouldn't expect a high potential pay-off without a little risk.
My most successful behind the lines operations were achieved with stealth (at east initially) not fire power.
Therefore, large maps (compared to force size) lend themselves to success, and maps with plenty of cover but where you can still move quickly.
You must consider where you are likely to come across enemy units (especially playing against humans) and choose to avoid these areas or approach from an advantagous direction with caution.
Use fast moving vehicles.
Have a place in mind where you want to reach before being discovered.
Choose the longer (covered) safer route to get there.
Use a fast armoured car for point. Other vehicles follow the same path, so you're less likely to be discovered.
If you take infantry along, be prepared to unload them, move them forward to engage and KO ATG or whatever, then load back up and move on.
If you get caught in a heavy firefight, and you're not near your objective. Just disengage, load back up and move out; take another even longer route this time. It may be a couple of turns before your opponent (assuming human) realizes you're gone; and this can cause even more panic and confusion for him, than if you were still fighting him.
When behind enemy lines, 'hit and run' tactics will keep your men the most safe and have the biggest psychological impact.
Your enemy may have to completely reshuffle his forces to react to...
You know what they say 'order, counter-order, disorder'.
The size of the force you send behind lines, depends on your objectives, the map, and what you can spare. There's pros and cons to small and large forces.
Here's screen shot of one of my large and successful sorties behind the lines against a human opponent.
http://img136.imageshack.us/my.php?i...attle8civ9.jpg
You can read about this battle here:
http://forum.shrapnelgames.com/showthread.php?t=31135
(it's post #8, Battle 8)
cheers,
Cross