In 2014, the Russian Federation conducted two separate phases of operations in Ukraine. Despite substantial differences in the objectives of and methods used within the operations, it is worth noting that their natures have much in common. Both operations were planned and conducted in accordance with the doctrine followed by Gerasimov and on the basis of the concept hybrid warfare.
NATO, for its part, has consciously and conspicuously de-emphasized nuclear weapons in its defense policy and posture since the end of the Cold War. As a consequence, the Alliance now lacks the policies and capabilities needed to deter, and if necessary to respond to, a limited Russian nuclear strike.
– Dr. Matthew Kroenig, 2015, US Senate testimony