Is there a direct link between what US President Donald Trump says and what Russian President Vladimir Putin does? Certainly, the harsh words and bitter violence of recent days in Ukraine suggest the answer is maybe.

Any analysis of Donald Trump's current thinking on Russia risks getting out of date very quickly.Read too much into an individual tweet, post or off-the-cuff comment by the US president, and the danger is that your conclusions will be contradicted by tomorrow's tweet,

I’m not happy with Putin ... because he’s killing a lot of people,” Trump said. He decided to resume weapons shipments to Ukraine days after the White House announced a halt.