I don’t see Russia’s Vladimir Putin as a threat. He has been backed into a difficult corner.
Russia’s economy suffers under economic sanctions, the Russian intervention in Syria isn’t going as well as hoped, and the Russian governmental structure is riddled with corruption.
But Russia has a nuclear force second only to the USA. Russia is the only national in the world with the power to bring about the mutual destruction of itself and the USA.
It is a bad idea to back Vladimir Putin into a corner in which he thinks Russia is threatened, over matters in which the United States has no vital interests.
President Obama says Putin is an aggressor. If so, he is a highly unsuccessful aggressor.
Russia’s position is much weaker than it was five years ago. Back then, Russia had good relations with Ukraine and it was integrated into Russia’s economy. Now the best Putin can hope for is continued Russian occupation of Crimea, a devastated eastern Ukraine friendly to Russia and a hostile western Ukraine.