Two essential points (taken from Reuters):
http://www.reuters.com/article/europ...s/idUSL8723679
1) Georgians don't live in South Ossetia.
"The majority of South Ossetia's 70,000 people are ethnically distinct from Georgians and look to Moscow rather than Tbilisi."
2) The US trained the Georgian military.
"Felgenhauer said Georgia's U.S.-trained army was stronger than many believed and had trained for just such a scenario."