Recon

Recon: When attacking or defending, recon can be the factor that make a significant difference.

Enemy sends big stacks at you figuring that they will win and then goes away from keyboard for a long time.

Only you reconned his force, so you know what is coming.

What can you recon with?

1) Armored cars

2) Air craft by patrolling long enough to identify the attacking units and their conditions. Works better if you have local air superiority. Currently works if you can get in and out before the enemy comes back online too.

3) Light tank (not the best but can sometimes work if the enemy doesn't have aircraft in the area

So, you reconned. Then you have to decide whether to attack, defend or run.

Infantry have a nice defense. If your enemy has put his large stack on autopilot and then goes away from keyboard, you may be able to put a stronger defensive force in its path and stop so that it attacks you. If you can get artillery to hit him from behind your force that helps as well.