The ground scale I use is 4cm=1km, so a battalion sized unit ideally has a base width of around 4cm, as one kilometre is the minimum frontage such a unit would occupy.
Leg infantry are mounted on 4x4cm bases like the Italians above, All photos have been taken against my cutting mat which is marked with a 1cm grid. Hopefully this will help give readers a better idea of sizes. The dark square at the rear left of the base is the mount for the unit's strength point (SP) marker. I'll cover SPs in a future post.
My older (veteran?) units are based on balsa (3/8inch thick from memory). I like fairly thick bases for two reasons: Ease of handling - which helps to preserve the toys and to help set the stand apart from the terrain - this helps to overcome the notion that a toy tank or whatever represents a real one. It doesn't. Rather it represents a battalion-sized unit of, say 40-80 tanks. All of this can really annoy self-styled 'proper' gamers. Do I look bothered?
In the case of Motor Battalions, Panzer Grenadiers and the like who have their own integral transport vehicles, I mount the figures and vehicles on the same base - as in the case (above) of this battalion from 21 Panzer Division. Vehicle bases are again ideally 4cm wide and can be as long as neccessary to accompdate the toys. In case someone asks, the plastic figures on this stand are accompanied by their Roco Steyr lorry. Very postwar but it somehow looks the part.
Some models end up on really quite long bases - such as this Flak batalion represented by an Sdkfz 7 (Roco) and trailer (Airfix), also on the strength of 21PD
More recent models have bases cut from foamcore board. This is about as thick as the balsa bases but a hell of a lot quicker and easier (and cheaper!) to cut. I use a steel safety rule and a Stanley knife with a fresh blade.
Some models - especially tanks and bigger guns need wider bases. This Pz Abt (Matchbox PzIII with resin turret) from 21PD needs a 5cm wide base. While we're dealing with tanks I should mention that I glue on the turrets. It's not a PzIII, it's a battalion... This too can annoy others!
When building units it is always best to consider what looks more or less 'right', rather than what is 100% accurate. A case in point is this Italian lorry. This is actually a 15mm (Peter Pig resin & metal) model, but the real thing is so huge that this toy looks OK with 20mm figures.
It is worth tailoring base sizes so that the finished division fits in a boxfile. It is evident from this photo that 21PD is a nice snug fit!Coming soon - SP markers.
Remember that if you'd like me to run a post on a particular Megablitz unit (or unit type) feel free to ask.