I was wondering, during ww2, what would be the optimum frontage for an Infantry Battalion/Regiment/Division? I know that terrain plays a huge role in the equation, but there must be a certain troop density where the men are not tripping over one another or so spread out that they are ineffective. I was reading about a thrust into Stalingrad being on a 3km front and was just wondering what formations that size front would contain, which is where the question comes from. I am more looking for a loose rule of thumb(if such a thing exists) that i can apply in future readings.
It really depends on the nationality of the units involved, the terrain, forces available, and the time frame. If this was a German thrust into Stalingrad, I would expect a 3 km frontage to be a regiment or so. In later war situations, the Soviets would pack a couple of regiments into a front this small, although their rifle divisions were also understrength.
So I guess that would be my rule of thumb - a regiment plus supporting arms, but it really does vary widely.