The Berlin Wall wasn't the only barrier to fall after the collapse of the Soviet Union and the end of the Cold War. Traditional barriers to the flow of money, trade, people and ideas also fell.
But as the arms-control scholar Thomas Schelling once noted, two things are very expensive in international life: promises when they succeed and threats when they fail.
(This picture is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license. - Photograph created by Larry D. Moore (Nv8200p on en.wikipedia) using a Kodak EasyShare P880 camera.)