After years of bluster and suggestions by Mr Putin that the US is a paper
  tiger, the Kremlin is now coming face to face with the cataclysmic
  consequences of what it has done by invading Ukraine and changing
  Europe's borders by force. By the same token, Washington needs to move
  with care since it would be a geostrategic miscalculation of the first
  order to push a nuclear-armed Russia too far into a corner, or to
  perpetuatue a cycle of grievance.