Russia has amassed more than 100,000 troops near Ukraine's border in recent weeks, according to US estimates, raising fears from Western and Ukrainian intelligence officials that an invasion could be imminent.
As frantic diplomatic efforts are made to avert war, analysts are warning that Russia's military poses an immediate threat to Ukraine.
But if an invasion were to occur, it is not clear where it would begin. Russia has created pressure points on three sides of Ukraine — in Crimea to the south, on the Russian side of the two countries' border and in Belarus to the north.
Here are the three fronts Ukraine and the West are watching, and the recent Russian movements detected in each.
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