Big Trouble in Little Former Soviet Union

So, Russian invaded Georgia the other day. I've been trying to pull myself away from the women's 10 meter air rifle competition long enough to find out exactly what in the hell's going on.

So, Georgie tries to reassert control over a province that doesn't want to be part of Georgia (and where many of those living in the province are Russian citizens). The Russians then invade Georgia, sending in ground troops, and conducting air strikes on multiple targets. Both sides are calling it a war. Everyone wants there to not be a war and is calling for a cease fire. The EU says they'll help everyone sort things out.

Now I understand why Russian would invade a sovereign nation and everything, but...oh, wait. I guess I don't understand. In everything I've read about what's going on, it doesn't seem like Russian's really offered up much on the order of an explanation. I understand that they have citizens in Georgia, but invasion? Not to cherry-pick examples, and I'm not calling this analogous, but there are a lot of Mexicans in California, but I'm not sure Mexico has a right to invade SoCal under any circumstances short of ethnic cleansing.

I'll keep an eye out in the coming days, but I think we should all stay tuned in the meantime. Even if it means skipping parts of the synchronized diving competition.