People trying to analyze the South Ossetia War need to remember that Russia didn't really need another reason to go to war in that region of the country. There are a number of breakaway regions in the South of Russia, and Georgia considers itself the regional hegemon of the area. Since Georgia has US backing, Georgia's interests are always suspect - the conflict could have broken out at the slightest provocation.
Although widely accepted that Russia opposed Georgian membership in NATO, I think the 2008 South Ossetia war was motivated by political conflict over South Ossetia. South Ossetia had been largely under control of a Russian-backed government, and Georgia launched a large scale attack to regain control of the territory. Russia responded with military action and both sides of the conflict escalated. Russia justified their actions by claiming Georgian forces had killed Russian peacekeeping troops in South Ossetia.