Why would putin do this unless he wants to attack NATO?
Russia put up a big tantrum over US anti-missile systems in the poorly negotiated New Start strategic nuclear weapons treaty Obama signed with them. They wanted limits on US ABM systems, which were, from what I understand, very weak language, with the threat of withdrawing from the New Start treaty.
Russia has a large strategic nuclear building program to re arm itself with big new multi warhead ICBMs which were suppose to go away with the new treaty, along with new bombers, cruise missiles and new ballistic missile submarines. Ours are all Cold War age.
I suspect Russia intends to use the new anti missile systems in Romania and Poland as the excuse to “break out” of the New Start treaty, leaving us badly outnumbered in strategic weapons. Obama’s legacy will in the end be strategic nuclear inferiority for our country.