His annexation of Crimea and military involvement in eastern Ukraine broke the settled pattern of post-Cold War relations in Europe.
The Russian military's increasingly aggressive patrolling and exercises on the margins of Nato have raised genuine concerns - even in a country such as Sweden - that a conflict with Russia can no longer be regarded as impossible.
Reluctant Nato governments are slowly increasing defence spending, and the US is taking steps to reinforce its forward presence in Europe.
Russia, of course, puts the boot on the other foot and blames Nato's expansion for its increased military readiness.
But this is a government widely believed to have sent its agents to poison an opponent in London, leaving a radioactive trail across the city.
Curiously then, the prevailing Western response to Russia's engagement alongside President Bashar al-Assad's government in Syria has been to argue Russia and the West potentially share some common ground.