Jens Stoltenberg, the secretary-general of Nato, said the alliance hoped to speed up the response time of thousands of its troops to allow it to react to a combat situation more effectively.
In October, it was reported Nato was preparing to station 4,000 troops on the Russian border with the Baltic states in its biggest military build-up since the Cold War. The troops will be summoned from nations across the alliance, including the UK.
“We have seen Russia being much more active in many different ways,” Mr Stoltenberg told The Times.
“We have seen a more assertive Russia implementing a substantial military build-up over many years – tripling defense spending since 2000 in real terms; developing new military capabilities; exercising their forces and using military force against neighbors.
Mr Stoltenberg refused to be drawn on the specific number of troops being put on alert, but Britain’s outgoing Nato representative Sir Adam Thomson said it was likely to be around 300,000.
Sir Adam said the aim was to find a way to mobilize the troops within two months, instead of the typical time of around six months
A Rand study had indicated that war games showed the need to add $13 billion in equipment and 3 armored brigades to prevent NATO from being overrun in hours to days
From the perspective of the North Atlantic Treaty Organization (NATO), Russia's threat to the three Baltic republics of Estonia, Latvia, and Lithuania — former Soviet republics, now member states that border Russian territory — may be the most problematic scenario for Europe. In a series of war games conducted between summer 2014 and spring 2015, RAND Arroyo Center examined the shape and probable outcome of a near-term Russian invasion of the Baltic states. The games' findings are unambiguous: As presently postured (in 2015), NATO cannot successfully defend the territory of its most exposed members
In 2017, the NATO European command will receive an armored brigade combat team, an artillery brigade and a battalion to stand up a division headquarters, if needed for permanent stationing in Europe.