Will Britain come on board in a big way? In recent years, Russia has raised $400 billion in stocks and bonds on the London stock exchange. Roughly 70 Russian companies are traded as depository receipts, and numerous IPO’s have been sold there. So if Britain closed its financial markets and its banks to Russia, the blow would be huge. Huge. The question is, will Prime Minister Cameron do it?

Another major source of Russian funding is U.S. mutual funds, with investments worth a reported $325 billion. Big outfits such as Pimco, BlackRock, Fidelity, Goldman Sachs and T. Rowe Price have served as the emerging-market investment intermediaries. And if that money were pulled, another gigantic blow would land on Russia’s finances and economy. The ruble would completely tank, forcing the Russian central bank to spend big chunks of those $400 billion in foreign-exchange reserves.

And then there’s Western bank lending to Russian business: $51 billion from France, $37 billion from the U.S. and $20 billion to $30 billion each from Italy, Germany, the U.K., and the Netherlands.

The point of all this is that the deflation of the Russian financial system and economy can be done through strict and severe banking sanctions. But those sanctions have to come from Europe as well as the United States.