LONDON — For close to a quarter-century there was a basic assumption in the West about Russia: It would, with zigzags and pauses, after huffs and hesitations, gradually integrate with the Western world. Whatever the misgivings in Moscow about the expansion of NATO after the collapse of the Soviet Union, this appeared to be the course set in the Kremlin, more energetically by Dmitri Medvedev, but even by earlier incarnations of Vladimir Putin.

From Berlin to Washington, the idea was that interdependence would grow. Russian membership (now suspended) in the Group of Eight leading industrialized countries was an important sign of the direction set. Modernity would do its work, breeding openness and connectedness. Autocracy and crony capitalism would yield over time (maybe even a long time, but still) to more representative government in Moscow and law-based markets.

This view of Russia, it is now clear, was wrong. Putin has decided on another course. He has opted for confrontation with the West as the basis for Russian development and the consolidation of his own power. Perhaps it was the street protests in Moscow of late 2011. Perhaps it was a perception of Western perfidy in Libya earlier that year. Perhaps it was some inkling about a moment of American weakness. Perhaps it really was the upheaval in Ukraine. Perhaps it was simply his inner K.G.B. officer rising to the surface as the years advanced.

In the end the reasons are secondary to the reality, which is that Putin has changed direction, igniting a wave of Russian nationalism. This is perhaps the greatest strategic volte-face of the 21st century, with huge and as yet scarcely digested implications. It is Putin who has pivoted to Asia, far more than President Obama, as Russia’s $400 billion gas deal with China this year suggests. He has lost interest in the West as the magnet of Russian development, portraying it rather as the flawed and predatory civilization against which a new Russia can define itself.