Many board games have been created to simulate past military conflicts. They are often created to explore "what ifs", alternative choices the opposing commanders hypothetically could have made at the time. A basic problem, of course, is that we have hindsight knowledge (though sometimes still incomplete) of what actually happened.
To simulate "fog of war" games sometimes hide the positions or strengths of opposing troops. More rarely the strengths of untested "green" troops are even hidden from their own commanders. Elaborate scenario start conditions also try to recreate the historical limitations faced by commanders at the time: troops hopelessly out of position or delayed due to political restrictions, surprise, disrupted communications, etc.
What these games rarely represent, however, is that commanders sometimes start with fundamentally different understandings of "basic game mechanics", such as the effects of mapboard terrain on movement, supply, and combat. Many historical battles have hinged on one side believing certain terrain was impassible by many unit types. The classic gaming example is the Ardennes forest at the beginning of both WW I and II. A "historically correct" gameboard for the French would show it impassible to mechanized units, while the German gameboard would show it passable. Since the "after the fact" map has the terrain passable, the French player will of course want to defend it accordingly. Thus the elaborate setup-rules necessary to prevent this and ensure at least the possibility of achieving the historical outcome. But here the most important element of surprise, that of one commander suddenly discovering his world-model is incorrect, is lost.
This limitation becomes more acute the further players try to maneuver beyond the historical outcome. Since these alternative paths were (figuratively and literally) never explored, we have little idea where their differing world models would have broken down in conflict with reality.