The tactic had been brutally effective in the past. This was the grim scenario that confronted the shah in 1977 when the Saudis flooded the oil market to rein in Iran’s influence. The 1977 flood was not the sole cause of the Iranian revolution, but it certainly was a factor: The shah’s rule was destabilized just as Ayatollah Ruhollah Khomeini mounted his offensive to replace a pro-Western monarchy with a theocratic state. In that sense, the oil markets fueled the rise of political Islam.

The price of oil also helped end the Cold War. Then, like Russia today, the Communist superpower was a global energy producer heavily reliant on revenues from oil and gas. In 1985-86, the Saudis’ decision to flood the market — which some believe was encouraged by the Reagan administration — led to a collapse in prices that sent the Soviet economy into a tailspin.

“The timeline of the collapse of the Soviet Union can be traced to Sept. 13, 1985,” wrote the Russian economist Yegor Gaidar. “On this date Sheikh Ahmed Zaki Yamani, the minister of oil of Saudi Arabia, declared that the monarchy had decided to alter its oil policy radically.”

Today, in Russia, fully half of government revenue comes from oil and gas. Even if oil returns to $40 a barrel — it twice fell below $30 earlier this year — that depressed price still creates “a dangerous scenario,” according to Mikhail Dmitriev, a former Russian deputy economic minister. Inflation in Russia hit double digits last year; its sovereign wealth fund, which bails out struggling Russian companies, is depleted; and factory closings are fueling labor unrest.

Unhappily for President Vladimir V. Putin, Russia’s fiscal crisis has coincided with his military interventions in eastern Ukraine and Syria. If Russia’s economy worsens and Mr. Putin feels cornered, he may look for ways to distract the Russian people with more rally-round-the-flag provocations, as well as induce panic in the oil markets about supplies and gin prices back up.

Future shock has already arrived for oil producers like Venezuela, whose economy has been gutted by lost revenues from oil, which makes up 95 percent of its export earnings. With inflation predicted by the International Monetary Fund to reach 720 percent this year, Venezuela has become a financial zombie state — a harsh reminder of what can happen to countries that rely so heavily on a single unstable commodity price. President Nicolás Maduro is at the mercy of the markets that, every day, nudge his tottering regime nearer the abyss.

Another oil producer, Nigeria, is running out of money, hobbling President Muhammadu Buhari’s campaign against the Islamist Boko Haram insurgents in the northeast. The plunge in oil prices has also shaken Central Asia, where Azerbaijan and Kazakhstan have expressed interest in emergency bailouts from the I.M.F. and other lenders.