Russia’s aggression in Ukraine marks a paradigm shift, the end of trust in the post-Cold War order. This order, based on respect for territorial sovereignty, the integrity and inviolability of borders and a belief that relations can be built on common values, has collapsed. International treaties no longer hold, and the use of raw force is again legitimate. In its annexation of Crimea, Russia has thrown the rulebook out the window. The world is back in a zero-sum paradigm. This is not about only Crimea or relations between Ukraine and Russia. The shift has changed the assumptions underlying European security and dealings between democratic states and Russia. . . .

NATO’s raison d’être is to defend its members and their territory. Steps must be taken immediately to ensure a NATO presence across the alliance’s territory. . . .

Recognizing that this challenge will remain for the medium to long term, a refocus on NATO’s core responsibility should be the aim of the September NATO summit in Wales. This must go hand in hand with greater investments in defense by European allies. Maintaining 2 percent of gross domestic product for defense must become a major benchmark of allies’ commitment. Allies in Europe need to wake up and realize that meeting that target is vital to giving credibility to deterrence and for revitalizing the transatlantic relationship. . . .

Russia has to pay a price for its aggression. This is a matter of credibility of the international order, an order that, if it disintegrates into the “anything goes” model, will wreak havoc on international relations and peace and stability. Policies of positive engagement with Russia must be reconsidered in a number of international organizations, including at the United Nations, the Organization for Security and Cooperation in Europe, the Council of Europe, NATO and the European Union. Our response to Russia should not be about the price of gas; it must be about respect for common values. Any economic sanction is cheaper than military intervention. Nothing costs more than the loss of freedom.

In years past, the transatlantic alliance has withstood some difficult challenges. Today, we face the most difficult one in generations. The lights of liberty are being extinguished in parts of Europe. We must take decisive and united steps to ensure that future generations do not question why nothing was done and why we didn’t act when so much was at stake.

Toomas Hendrik Ilves is president of Estonia.

Image: Unidentified gunmen at Simferopol Airport, Feb. 28, 2014 (photo: Elizabeth Arrott/VOA)