The Washington Post attempts to put together a timeline of how the Russia-Georgia war started. It gives a pretty good outline of some of the pre-war duels that took place before the introduction of armor units.
Like any battle, there is a definite fog of war that shrouds the events. We may never know the full timeline of events.
A U.S. official familiar with intelligence from the region said the administration could not put a time on the Russian move into South Ossetia. “It’s not clear,” the official said. “You’d have to have had somebody there with a stopwatch, and something overhead at precisely that moment.”