You have the option of asking your allies to attack other races, which is useful if you are at war and want to get some help from your spacebuddies.

However, there should also be a request to your allies to make peace with a race they are currently at war with. I noted this because I was allied with two races that were constantly at each other's throats, leaving me stuck in the middle getting bleep-bleep messages every five minutes. "Help, the Squig Empire is attacking us!" "Help, the Hoggiraptor empier is attacking us!" I couldn't help either without breaking an alliance so I just let them fight it out, but I would have been happy to drop a couple million sporebucks so they would just leave each other alone!

Can't we all just get along?

(My other option, of course, would be to obliterate both empires... but I was trying to be a nice friendly alien for once.)

ahh no war in fun
boom boom you are all dead

Galactic Civilizations II lets you.

But GalCiv II is by Stardock, so I'd expect it to be better.