RUSSIA | UKRAINE
Dr Jack Watling, of the Royal United Services Institute, says: "I think the Ukrainians are in a very difficult position." He's just returned from Ukraine and says the country's military leaders now face some "very hard choices". Western officials estimate that Russia had up to 190,000 troops on Ukraine's border - far more than Ukraine's entire regular army of 125,600. Russian forces are already crossing the border from multiple directions. Ukraine will find it hard to defend thousands of miles of its frontier - from Belarus in the north all the way down to Crimea in the south. If you think of Ukraine as a clock face, the Russians can mount attacks from 10 o'clock to 7 o'clock.