To add to what Rae has said, I'd like to point out that this is the perfect job for PCs to undertake when they finally reach allied lines.
The local commander sees that they are a homogeneous unit and gives them an official classification, such as '22nd Redoubt Company' or whatever. A strong terrain feature is allocated to them and they are ordered to go there, recon it and identify threats, strategic and tactical features, resources and anything else. Then they are given intel where likely sources of defensive equipment may be located. New PCs can come in as drafts of personnel from the parent unit, and some forms of divisional or battalion support might be available.
Better yet, the division will have secured a rear area territory of importance; possibly a civilian urban or manufacturing centre. This makes an ideal town environment for the PCs to kick back, wheel and deal and get into fist fights with other units, all under the watching eye of MPs with the threat of a night in the guard house waiting. A definite worthy addition to a campaign as a change of pace. Disease can make the place off limits if the GM feels it detracts from the feel of the game.
The GM should map out a grand strategy for the unit, incorporate it into the regional strategy that does need to be as detailed as well as an OPFOR strategy. These two strategies can ebb and flow, providing a living back ground of reverses and victories that the PCs can partake in beyond their own local concerns.
ChalkLine likes firebases
