Russia’s predictable invasion of Ukraine is the result of a combination of factors, each of which must be taken into consideration as the West figures out how best to respond to what could easily become the most bloody conflict Europe has seen in decades.

The first and most important factor is, of course, Russian dictator Vladimir Putin’s ambition and aggression. He always intended to invade Ukraine and piece back together the dissolved Soviet empire — he made that clear in 2008, when he invaded Georgia, and again in 2014, when he invaded and annexed Crimea. He has been waiting for the right moment to continue his expansion ever since. And on Wednesday, that moment came.