Ukraine-Russia crisis: How soon might a war be and what would it look like?

The Ukraine crisis is the classic case of a known unknown: We know that we don't know what Russian President Vladimir Putin intends to do as he amasses troops on the Ukrainian border.

So how imminent is the threat of a full-scale war? Some fears appear to have receded slightly following key talks that included Russian and Ukrainian officials. But the Pentagon also says the Russian troop buildup continues, and President Joe Biden told his Ukrainian counterpart Volodymyr Zelensky on a call Thursday that there was a distinct possibility Russia could launch an invasion in February, according to National Security Council Spokesperson Emily Horne.

Zelensky, however, restated his position that the threat from Russia remains "dangerous but ambiguous," and it is not certain that an attack will take place, a senior Ukrainian official told CNN. Diplomatic efforts to defuse the crisis continue.