If you fight so as to keep your route to the rear generally clear, then you probably don't need to use it.
However - setting one for the entire force, to the rear and ahead of the baseline may help, as retreaters might pause there. However - most routers even have usually pulled there act together even before then, so it would really only help if your force was totally broken (and you headed the HQ there to aid with rallies). In which case the game is probably over, and you are thinking of salvage more than anything else (vs. a human opponent especially).
So - its most use for any formations which have looped round into the rear of an enemy with real fight capacity left in them (as opposed to a herd of routing grunts
).
Andy