For months, the West has struggled to take a strong stand against Russia for its incursion into Ukraine. And while Europe's leaders are acutely aware of the threat to peace on their Eastern flank, the countries with the most at stake have, time after time, seemed unable to present a united and resolute front.

But the downing of Malaysia Airlines Flight 17 has become a game changer -- a watershed moment which most concede would be too dangerous to let go. And now, as Europe prepares to finally take decisive steps, its chiefs will have to recognize that, if they are to be effective, they will also have to hurt their economies.

As a block, the European Union exports about 100 billion euros worth of goods and services to Russia and takes in roughly 200 billion euros of the latter's imports.

That is money that matters, for sure, but it's not Russia's role as a consumer that would affect Europe most. Rather, it's Russia's function as a major supplier of energy. Should Russia cut its gas to the West in response, the loss in European production would more damaging than the hit its trade balance would take.

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