Question: How much planning would it take to send two armored columns into a hostile country? Lets say with 400 tanks?
Answer: Many months of planning and supply.
Question: How many Russian tanks have been destroyed?
Answer: Initially Georgia reported 40 Russian tanks destroyed. We all doubt those figures. Still Georgia did hold up the Russian column at the border for a good while considering. If the US has lost 20 tanks, it would be huge news. Russia also lost at least 2 jets confirmed. Possibly several more. I assume Georgia has been supplied with some really nice anti-tank and anti-air systems. Until they were overwhelmed, it looks like they worked well.
<opinion> There is a long game to all this. Putin is attempting to bring down the Us the same way the US brought down Russia. Putin will sit on the pipeline until he is pushed out. Note that the pipeline is closed in Turkey due to an attack by Kurds. but the oil is being off loaded at Georgia ports. that is until Russia bombed the ports and put them out of commission.
Cut the oil pipeline. The price of oil goes to $200 and the US fails. If Europe gives aid to Georgia, Russia refuses to sell oil and gas to Europe. Putin holds all the cards on this one.
Israel and France are big players. Expect action from France first. Israel will supply defensive systems covertly. The war and occupation in Georgia will go on for as long as it takes to bring the US to it's knees. (economically speaking)
</opinion>
Here is a good write-up of the players and stakes in this game.
http://szamko.gnn.tv/blogs/17155/Pipeline_Time