Now Russian officials have to make difficult choices, none of which are good. As the ruble has collapsed, many individuals and businesses have been trying to take money out of the country or spend it; the International Monetary Fund estimated in October that about $100 billion could leave Russia by the end of the year.

The Central Bank of Russia has tried to stem that tide by raising interest rates, which in turn slams the brakes on an already fragile economy. Some analysts believe that Moscow will soon have no choice but to impose capital controls, a move that would further isolate Russia from the rest of the global economy.

Russia has large financial reserves — about $420.5 billion at the end of November — but some of that money is tied up in gold and sovereign wealth funds that cannot be tapped easily to defend the ruble, says Anders Aslund of the Peterson Institute. While the government does not have a large external debt, many Russian banks and corporations, including large oil and gas businesses, were on the hook for about $614 billion in foreign currency borrowing at the end of September. Some of those firms will struggle to repay their loans if Russia’s economy deteriorates further and oil prices stay at current levels or decline further.

Mr. Putin has taken great relish in poking the West. Now that he is in trouble, the rest of the world is unlikely to rush to his aid. On Tuesday, a White House spokesman said that President Obama intends to sign a bill that would authorize additional sanctions on Russia’s energy and defense industries. That bill would also authorize the administration to supply arms to Ukraine’s government.

The sensible thing for Mr. Putin to do would be to withdraw from Ukraine. This would bring immediate relief from sanctions, and that would ease the current crisis and give officials room to start fixing the country’s economic problems. The question is whether this reckless leader has been sufficiently chastened to change course.