The tragedy of Ukraine still has a long way to run, and much about its trajectory and outcome still remains unclear. But one thing we do know is that deterrence failed.
The clear threats and warnings made by America and its allies as Russian military forces mustered on Ukraine's borders did not dissuade President Vladimir Putin from launching his invasion, for reasons that are all too plain. As far back as early December last year, President Joe Biden said direct US combat involvement was not on the table. And now we know that once he had ruled out a US military response, the economic and diplomatic punishments threatened by Washington and its allies were not enough to make Mr Putin back down.