So, everybody knows that in an RPG, PCs have near-omniscience regarding the battlefield, but the impression I get from reading real-world history of battles tends to suggest that once a fray was entered (especially historically) all you really can see is what's in front of you. For those of you who read comics, Brian Wood's EXCELLENT Northlanders 3: Blood in the Snow has a quote about being in a shield wall, and feeling something warm running down your leg, and not being sure if it's the piss of the man next to you or your own blood. I love the idea of the failure of the formation, the fear of battle, and the total unawareness of what is going on behind you.
I'm sure this has come up before around these parts, but does anyone have any recommendations for specific games, houserules, or anything else to add a bit of "fog-of-war" to RPG fights? Something mechanical to drive home the idea to the players that they have very little knowledge of the proceedings around them.