This was a profoundly weak country to begin with. Russia’s GDP equals that of Italy. Its population is small (140 million) and declining: More than 500,000 citizens have fled over the past three years, and life expectancy is falling. The level of corruption is staggering. Russia’s oil fields are mature and require capital and Western technology even to keep production flat. Neither of these inputs is available now. The liquid portion of Moscow’s foreign-exchange reserves, which the Peterson Institute has estimated at roughly $200 billion, is not large relative to the $33 billion that was spent in December to defend the ruble.

Many Russia experts note the deep and sad capacity of the Russian people for suffering. They point out that Mr. Putin’s popularity, boosted by the annexation of Crimea and the Ukraine conflict, is nearly 80%. They therefore conclude that he is not sensitive to economic and financial pressures.

But Russia is not North Korea. It is a full participant in global financial markets. Its currency is traded globally, as is its stock market, and its corporate sector borrows externally in large amounts. There is a point at which a currency or banking collapse will prevent any major nation from functioning.