It'll work against the AI just fine. I've pulled it off on human opponents before but it's quite rare.
Usually after a very extensive battle, they'll start getting sloppy. If you've ever been in a game lasting
several hours on end, you'll know what I'm talking about here.

For best results though, it's better
to launch a three prong attack. Even if the odds are against your assault forces, it's all about the
distraction. That second or two could shift the tide of the battle in your favor, or not.