Putin reaches out to Obama as Russian troops continue to mass on Ukraine border (warning:Stupid autoplay video)

The increase is due to the continued arrival of logistical units - for instance, field hospitals - that would be needed to sustain operations. The intent of the buildup is still not known but the Russians have assembled “all the elements of combat power” needed to invade, according to officials.

Analysts have come up with four potential scenarios that could unfold, Martin reports. First, the Russians could cut all the way across Ukraine to the pro-Russian enclave of Transdniester in Moldova; second, they could try to take Kiev; third, they could take the predominantly Russian-speaking cities of southeastern Ukraine; and finally, they could take the cities necessary to establish a land corridor to Crimea.

Russia has the forces to execute any of these scenarios, Martin reports, and they are ready to go with little or no notice. As with all buildups, a military force can only sustain a peak level of readiness for so long before it starts to decay - the old “use it or lose it” syndrome. They could use it by invading, conducting an exercise or standing down.

That would fit with Putin’s mention of the blockade of Transdniester in the phone call today. Damn, sweeping all the way across southern Ukraine would be quite a bold move.