Fiona Hill has a special vantage point on this slow-rolling crisis that US officials say could bring war in Europe at any moment. As a White House national security aide, she advised then-President Donald Trump on Russia and Ukraine – and became a star witness in impeachment proceedings that resulted from his conduct.

After Trump deferred to Russian President Vladimir Putin over the US government’s own intelligence agencies, Biden has deployed those agencies’ tradecraft in a multi-pronged transatlantic effort to deter Russian aggression.

“You couldn’t get a sharper contrast,” Hill observed in an interview.