Putin's interests lie in retaking territory on his borders. He has the conventional means to do this, and we (NATO) have neither the means nor the inclination to do much about it. At best, we would impose sanctions. Oops, we've already done that.....
Russias conventional forces are vastly inferior to Nato in both number and quality. After the decades of decay of the Soviet period, Russian through years of further economic decay and only recently tried to modernise.
Why would you think Russia's military is capaable of anything?