There's usually no reserve up to company level in many armies; instead, the combat troops are meant to be capable of counter-attacks without a dedicated reserve. That's more responsive.

A battalion reserve is often not much more than a platoon, if there's any at all (a Verfügungsplatoon - a platoon directly under command of the Bn Cmdr - is an enticing idea from the Cold War; it could serve as recce Plt, as couriers, as HQ guard, as traffic organizers, as CO escort and as Bn reserve).


The share of reserves grows on formation levels, unless these formations are overstretched (on the other hand some experts think that reserves are even more important the more you're overstretched).