Generally, the ratio for an attack is 3-1, with the attacker on the up side of that ratio. This is mainly for an attack against a dug-in and fortified foe. The force ratio calculator is a pretty good tool, but even it states in a disclaimer that it does NOT represent any sort of guaranteed chance of success in a battle!
Anyway, on to KB's comments about politics and such. In my job, I, and the rest of my associates, are a bit unpopular around here with some of the powers that be for the simple fact that we are trying to utilize off-the-shelf commercial simulations in the classroom to support common-core warfighting concepts and skills. Many don't like that for the simple fact that it means less Contractors running over-complicated simulations in expensive exercises to teach a simple concept.
Our scenarios are designed only to meet certain criteria - order of battle, location, and, if needed, historically representing units in the OB. The rest is up to the instructor to work with. If he/she wants to ensure the "good guys" win, then so be it - it's out of our hands.
Therefore, the politics of simulation wargaming is out of our hands - we teach the instructors and students how to run the appropriate simulation, help them to develop scenarios, then provid "GS" level support during the exercise, fixing things that break and such.
Now, if you want my $.02 on the subject, then I will say this. The whole arena of simulations in the military is being killed by too many different programs that don't talk to, or "stimulate" each other. It is also rife with mismanagement, territorialism, and the desire to intentionally provide faulty simulations or sims "too difficult for the average bear to run". This guarantees the contractor a lock on providing current and future support per an overestimated and vaguely-worded contract.
Can you tell this is a sore spot with me? ;-)
Don't get me wrong, I absolutely love what I'm doing here, and I thank God every day for my fortune, but it is sad to see the "same-old, same-old" happening here, supposedly on the cutting-edge of military education.
Our shop has found that we can train more people, more efficiently, and with more student/instructor interest and retention of concepts than with any of the "military" developed simulations, only using 2 or 3 commercial sims costing less than $40 each.
Yes, we are despised by many, but a proud and haughty bunch are we!