I'm sure this has been asked before, but I coulnd't find it. If someone has massive amounts of offensive figs protecting a planet, is there a least painful way to clear them out?

In an unlimitted game, someone stole my planet while I was on vacation and then plopped a couple million figs over it in offensive mode. There hasn't been time to finish any citadels on it, so I know that other than the figs, it's essentially defenseless. Is there really any decent way to get rid of those figs? TIA.

--smthng

"All your planet are belong to us!"