I've been busily writing an article for Game Gems 6, entitled QJM Engagement Analysis. QJM was invented by T.N. Dupuy and even though the model is fairly simple (mathematically!) it still allows for some insanely interesting simulations. I played around with the Lanchester equations a bit and they seem so contrived; for example forces that engage have to have the same unit composition? What!?? Nonsense. The QJM system allows for different unit compositions, weapon compositions, technical compositions and also includes alot of "variable" behaviors that we need in computer games development.
This system is also plug and play - which means you do NOT have to use all the variables; you just have to be consistent from one force to the next.
Believe it or not - after playing the majority of turn based strategy games and rts's over the last 2 decades, a lot of computer games programmer use a model like this whether they know it or not.