Lowering the threshold for the use of nuclear weapons, Russia has said it reserves the right to hit back with nukes in case of an aggression ....

which may be a veiled warning to China and rising NATO powers.

“Russia reserves the right to use nuclear weapons in response to the use of nuclear and other weapons of mass destruction against it and its allies, as well as an aggression against the Russian Federation with the use of conventional weapons jeopardising the very existence of the state,” a military doctrine signed by President Dmitry Medvedev said.

Expansion of NATO closer to the boundaries of Russia, deployment of missile shield elements on the perimeter of its land and maritime borders, international terrorism, proliferation of WMD and growing number of nuclear powers have also been identified as the external threats for the security of the nation.
The Hindu : News / International : Russia unveils new nuclear doctrine