Vladimir Putin’s biggest enemy right now may well be the currency markets.

Even as it spars with Ukraine, Russia’s government is in the midst of a full-scale war to preserve the value of the ruble as a plummeting oil price has led to billions flooding away from the country. The ruble fell 11 percent against the dollar on Monday alone.

To try to stanch the bleeding, on Monday evening (the middle of the night Moscow time), the Central Bank of Russia announced a stunning interest rate increase. Its main deposit rate is now 17 percent, up from 10.5 percent when Russian banks closed for business Monday.

It may go without saying, but an emergency interest rate increase of 6.5 percentage points announced in the middle of the night is not a sign of strength. Rather, it is the kind of thing you see only in an old-school emerging markets currency crisis. And that is very much what Mr. Putin’s Russia is now experiencing.