How NATO's eastward expansion set the stage for the standoff in Ukraine

The current standoff on the Ukrainian border began when Russian President Vladimir Putin provoked fears of an invasion, but the roots of the crisis go back decades.

Russia and the West have been at odds about the role of NATO in Europe since the fall of the Soviet Union. In the 1990s, some American diplomats warned against the military alliance's eastward expansion.

Here & Now's Scott Tong speaks with Emma Ashford, senior fellow at the Atlantic Council's Scowcroft Center for Strategy and Security.