The most common cheats are:

1) Reloading the game and redoing the same battles to obtain better results,

2) Turning off hidden units (can be done in version 1.0; DOS),

3) Playing with a custom dataset.

4) The good ol' hexediting trick.

How can I tell if my opponent is cheating?

Well, if he is using method 1), then youīll probably notice some extraordinary battleresults - e.g. he never seems to get a rugged defense. The same thing could be caused by method 3. If he uses method two, then you may notice, that your opponent always knows exactly where your units are. He will have his units race forward into unspotted territory, stopping right next to one of your vulnerable units and hitting it.

How can I prove that he is cheating?

As far as I know in most cases you canīt. There is one exception though: if he is using method 2 and is attacking a ground unit in unspotted terrain with ONE airunit, then it is a definate proof of cheating since it cannot be done with hidden units on.

Are there any countermeassures?

None that I know of. I suggest you find an opponent you trust.

What should I do then? Should I accuse him right away?

Thatīs up to you and your temper, but usually that will do no good. It will just lead to hostilities (via e-mail..?). It may be worth noticing what I observed; that cheaters donīt always regard what they are doing as cheating. E.g. method 1) may be a bad habit from the AI campaign and he sees no evil in evening out the combatresults to match something like what could be expected.