Relations between the Soviet Union and NATO countries dramatically improved in the late 1980 and early 1990s, bringing a decisive end to the Cold War. After the USSR collapsed in late 1991, the relationship between Russia and Western countries remained close and cooperative. But in the latter half of the 1990s, ties began to deteriorate. With the rise of Vladimir Putin at the end of 1999, Russia's relationship with Western countries became more precarious. Although cooperation still occurred, tensions began to increase. From the time Putin began his third term as president in 2012, the relationship between Russia and the West turned increasingly sour. Relations deteriorated still further after Russia forcibly annexed Crimea in March 2014 and sent troops into eastern Ukraine to foment an insurgency and ongoing war. Today, nearly three decades after the Cold War ended, Russia's relationship with the West is tense and conflict-ridden. What went wrong? Is there any hope of restoring East-West ties to a more cooperative footing?

Professor Mark Kramer is the Head of the Cold War Studies Program at Harvard University and the editor of the Journal of Cold War Studies.