My reponse wouuld be pretty much a mix of what everyone elase has said before on this post.
I try to avoid straight encounter or attack/defence battles, either using a specific scenario or at least adding some form of unceertainty (e.g. seni-random arrival time for reinforcements or having to roll for activation/observation of guards in a night attack, as per my Christmas game against Dr De-Ath).
For most of my games there are only somewhere between 5 to 8 'elements' per side (where an element could be a troop unit, an independant main character (MC), a vehicle or some other 'toy'). This ensures a gamme that can easily be fought to a conclusion in an afternoon or evening.
Example of a typical force for a small game:
Commanding officer - Independant MC ('Adventurer')
3 x 10-man troop unit - 8-9 Extras with rifles + 1-2 MCs, e.g. officer ('Leader' with pistol) + sergeant ('Veteran' with rifle)
one of these units could be cavalry
one of these units could be armed with anti-vehicle weapons - e.g.:
* replace 1 riflemen a heavy-bore anti-vehicle rifle team
* replace 1 or 2 riflemen with flamethrowers
* replace 1 rifleman with a heavy-bore anti-ironclad gun (Leviathan Gun in my world) - a second riflemman acts as his loader
* all rifle-armed troops also have magnetic bombs or torpedo lances
1 x armoured vehicle with medium gun (crew)
1 x 'toy' - e.g.:
* MC in steam powered armoutr with gatling gun
* large armoured automaton with operator (operating as one 'unit')
* 2 or 3 smaller automatons with operators (operating as one 'unit')