Putin may be willing to literally kill off all the adult men in Russia of ANY age in order to take Ukraine back into the Russian Fold

 So, not only is he likely to kill off most Russian men if he does this but also kill off most Ukrainian men defending their country too. Russia in War has never been efficient they have always been more brutal than anyone else. This is why Russia still exists today.

Their policies have always been scorched earth policies where any group resisting them are completely wiped out to the last man, woman and child.

This is what they are doing now in Eastern Ukraine as well.

How this all turns out 5 to 10 years from now must be considered from the point of view of Putin taking Crimea from Ukraine in 2014.As long as Putin is running Russia he likely will be killing Ukrainians as long as he is able to at this point.