Dulling Putin's knife and ending the Ukraine crisis peacefully depends largely on the EU. Sanctions will not impress Putin (he and his cronies are isolating Russia economically and financially more effectively than most sanctions could); peaceful yet tangible political steps within Europe will.
Polish Prime Minister Donald Tusk has made the right suggestion here: prompt establishment of a European energy union, starting with the market for natural gas and including joint external representation and a common pricing policy. This step, combined with further differentiation among supplier countries and progress toward implementing renewable-energy technologies, would invert the balance of power between the EU (Russia's most important customer for oil and natural gas) and the Kremlin.
Read MoreSanctions revive hunt for Putin's secret fortune
If, at the same time, Poland resolved to join the euro at the earliest possible opportunity, Putin's challenge to Eastern Europe would receive a powerful and completely peaceful answer. And Poland would assume the role of a major player at the center of an increasingly integrated Europe.
It has largely been Germany that has opposed integrating Europe's energy and natural gas markets. After the tragedy in Ukraine, no one in Berlin will be able to defend this stance, particular given that Germany's leaders do not want to confront Russia through sanctions. There will no longer be any room for excuses about why an energy union should be rejected. Everyone knows now what this communality called Europe is about. To borrow from Aesop's "The Braggart": Hic Rhodus, hic salta! Enough said, Europe. Now show us!
Commentary by Joschka Fischer, Germany's foreign minister and vice chancellor from 1998 to 2005. He was also leader of the German Green Party for almost 20 years.
Copyright: Project Syndicate, 2014.