This may sound weird, but Civilization IV is an excellent war simulator. Although the focus is far more on the strategic, rather than the tactical aspect. In Civ IV, the challenge is in the production of ones army while balancing scientific and cultural progress, and the strategic and diplomatic decisions in how to use said army. Turning all of one's citing into wartime production can be fruitless if the enemy dedicates himself to research and garrisons his cities with few but technologically advanced units.
As a turn based strategy game, the actual stat-based combat results are more a function of the quality of one's units, and the decision to employ certain units dynamically. For example, the high attack value of modern armor or mechanized infantry may be useless when attacking a city or garrisoned "tile" without the aid of siege weapons (artillery, ect) or naval/aerial bombardment to reduce the cities’ defenses and cause collateral damage before an initial assault. Your hard-earned state of the art army may be also be reduced to nothing by enemy airpower if it does not include AA units, as another example.
Because your nation begins around 4000 B.C., however, you do have to enjoy the empire-building and managing process before any successful campaign can even be considered. The fun of the war aspect in this game is based for more on the reward of one's efforts to create the army, and in the satisfaction of destroying or conquering those who gave you crap in the past, rather then its actual deployment and use IMHO. There's nothing like making a bee-line to the gunpowder tech and assaulting one's pesky, technologically-inferior (and heathen!) neighbors with Musket men. After reducing several of your neighbor's cities to rubble (with puny archers as their best defense), their leader may come begging for capitulation on terms of vassalage. Oh and you can force them to convert to your religion. Then you can make him your pet, or destroy him outright. It is also quite fun to sabotage enemy production prior to declaring war, like cutting off his access to strategic resources needed for the best units.
If you have never played this game, think of it like a game of chess where you also manage the production of new and better units.