In 2008 Putin began to modernize his military with Oil money

When he saw that the U.S. and Europe were weakened by the Great Recession in 2008 he decided to take advantage of this starting first in Georgia, then Syria and then Ukraine to try expand Russia's reach to where it once was during Stalin administration of the Soviet Union.

begin quote from page 33 of the Time Magazine with Putin on the cover as Czar from the middle of the page:

"NATO remains a military alliance, and we are against having a military alliance making itself at home right in our backyard or in our historic territory," he told Russia's parliament in March.

Putin was determined to reverse such slights and restore Russia's place in the ranks of great powers. That has become an easier idea to assert than it was a decade ago. A surge in global oil prices to more than $100 a barrel brought billions of dolars into Russia's oil-producing economy, even as the U.S. and Europe were weakened by the 2008 global economic crisis. The cash helped plug holes in an outmoded Russian economy. It also allowed Putin to modernize his military.

Putin then grew bolder. Some of it came in the form of cartoonish machismo:the shirtless horseback rides, the sjudo matches and other antics for the camera. The restoration continued. In 2008, Putin defied Western condemnation and sent his army into the former Soviet republic of Georgia, ostensibly to protect a pair of pro-Russian breakaway Republics---but likely also to punish Georgia's President, Mikheil Saakashvili, for having cozied up to the West. When Saakashvili told Putin that the U.S. and European officials were issuing outraged statements, the Georgian told Time in March, Putin recommended he roll up the papers and "stick them in their ass."

end quote near bottom center of page 33 of the Time magazine with Putin on the cover as "Czar".

So, the present Putin Stance of the Russian Government is not haphazard but rather part of a concerted plan to take back the old territory of the Russian Empire under Stalin and other Russian leaders in the past.

So, I would expect the Russian military adage, "Push the Bayonet in and if there is no resistance keep right on pushing. But, if there is resistance pull back" to be followed to the letter.

In other words if Putin is not confronted militarily he is going to keep right on going until he reaches France and Spain and Portugal, one city at a time over the next 10 years or so just like he has taken Eastern Ukraine and Crimea already. He will continue as long as he has the support of his people. However, if thousands to millions of people start dying along the way he is going to lose that support. So, Europe, NATO and the U.S. have to stop him one way or the other.