Skirmish against the AI in this game is terrible.
First you have the unit/building limit, so you can easily get stuck and not be allowed to build more. But you can use the Loader program to fix this.
Then when you do this the AI builds like crazy and easily runs out of resources, without even building an army. You can help them a bit by selecting starting resources to 10000, but then they end up just focusing on nukes.
It's like they put no thought in it and after some very challenging campaign missions skirmish is very disappointing to play against the poor AI.