Starcraft AI blog

Left to itself, a group of units sent across the map will tend to string out into a line, often with gaps. If that line runs headlong into waiting enemies, it will be eaten alive. The enemy “crossed your T,” as in battleship tactics. The whole enemy force can fire, while only the front units of the approaching line can engage, so you get defeated in detail.

Some bots keep their squads in compact formation as they move. They stay ready to engage any enemy that may suddenly appear. Other bots don’t care. They let their units string out and take the risk of being caught off guard.

AIUR is an example of a bot that doesn’t care about formation. It will happily attack in single-file and be ground up like sausage. In fact, I think that’s one of the main ways that it loses won games: Instead of gathering up its superior force and attacking with a coherent army, it fights with dribs and drabs as they arrive.

A number of terran bots that train marines and medics let the two get separated. The marines and medics form up into a squad and set out for a distant destination. Along the way, the marines find something to shoot at and stop to do that, while the medics continue on to the original destination. Separated, of course, they all die.

Exceptions. Letting units string out into a line is not always bad. If you’re in a hurry, then run run run at full speed. Staying compact would mean slowing down.

The line formation can be good.

Run your line of units parallel to the enemy formation, and when you’re in position, converge on them. In human play, this tactic is common with zerglings and zealots, whose melee attacks are most effective when they approach in shallow formation across the breadth of the enemy army. I haven’t seen any bot do this skillfully, even though it’s basic micro. For example, lining up zealots is key to breaking a terran tank push.

Tomorrow: The old terran bot Nova keeps its squads compact while moving. I’ll look into that.