Locking Zones of Control: Do you use them?

[JDR Dragoon]

A battalion of 600 men would be able string out a front of 3km but certainly not a position of 9 sq. km.

You don´t "string out" IRL. You dominate the ground by fire from mutually supporting and interlocking positions, primarily utilizing heavier weapons such as machineguns and mortars (plus autocannons and ATGMs, which might be vehicle mounted, in the MC series). Most WW2 battalions would expected to be able to man a 3 kilometer frontage fully and be able to hold it against all comers, holding at least a company or two in positions in depth behind the frontline companies (depending on whether the battalion has 3 or 4 rifle companies). And with that depth and reserve comes the ability to dominate terrain to the sides and rear by the shifting of fires and/or men to alternate targets and positions. This is how you dominate a position of 9 sq. km. (IRL you would of course not be able to direct an equal amount of fire outwards from each part of the position, but the game isn´t really detailed enough to reflect this).