Anxiety over a nuclear exchange between super powers seems out of place in a post-Cold War world where conflicts are usually fought within states, rather than between them. But despite the changing nature of the times, nuclear weapons continue to play a central role in Russian military strategy.

Last week, as thousands of Russian troops streamed into Ukraine, Putin issued a statement reminding the world that Russia was a nuclear-armed power.

"Russia is one of the most powerful nuclear nations," he said. “This is a reality, not just words.”

Putin is certainly playing up the threat of his strategic arsenal. This month, Russia is conducting a massive drill simulating the defense of its strategic nuclear sites that will involve more than 4,000 soldiers. And as columnist and historian Anne Applebaum recently noted, commentators in Russia are now claiming that Putin is "weighing the possibility of limited nuclear strikes" against targets in Eastern Europe, at least creating the impression that the Russian president is keeping his options open.

The situation recalls tensions between the USSR and the U.S. during the closing decade of the Cold War.

In 1983, relations between the U.S. and the USSR were under almost unprecedented strain after the Soviet invasion of Afghanistan, Olympic boycotts, and increasingly hardline leadership in Moscow. Both sides began to put into place new intermediate-range nuclear weapon systems that could reach a target in only a matter of minutes.

"Both sides now are putting weapons in to place that can reach each other in seven, eight minutes," Tom Nichols, a professor at the Naval War College, told National Geographic. This reduced "the amount of time for a decision about whether or not to begin a nuclear war, about whether or not to incinerate the entire northern hemisphere from minutes to seconds."

To deter the possibility of a U.S. nuclear first-strike, the Soviets created a system called Perimeter, also known as "Dead Hand."

The Dead Hand was a computer system that could autonomously launch all of the USSR's nuclear weapons once it was activated, across the entirety of the Soviet Union.

U.S. D of Defense map of Soviet intercontinental ballistic missile (ICBM) bases as of the 1980s. Wikipedia

Dead Hand was a weapon of last resort. It was created to ensure that even if the Soviet leadership was wiped out, a nuclear response could still be launched against the West and NATO in retaliation.

After Dead Hand was activated by Soviet military officials, "the first thing it does is check the communication lines to work out if there's anyone alive and in charge of the Soviet military," Alok Jha, author of "The Doomsday Handbook," told National Geographic. "If they're not alive, it takes over."

If Dead Hand did not detect signs of a preserved military hierarchy, the system would perform a check for signals of a nuclear attack, such as a change in air pressure, extreme light, and radioactivity.

If the system concluded that a nuclear strike had taken place, Dead Hand would proceed to launch all of the remaining nuclear weapons from all of the silos throughout the Soviet Union at targets across the Northern Hemisphere.

Of course, no system is fool-proof, and there are concerns that Dead Hand could still operate at some level within the modern Russian military and accidentally trigger the launch of Russia's active nukes.

"We've since asked the Russians if it's still on," Nichols writes at The National Interest, "and they've assured us, with complete confidence, that we should mind our own business."

Russia's Modern Reliance On Nuclear Weapons

Charts and statistics detailing past U.S.-Russia arms treaties and nuclear arsenals as of 2010. REUTERS

There's a possibility that Dead Hand was dismantled when the Soviet Union fell — but nuclear weapons are still an integral part of Moscow's defense architecture, even without a semi-automated doomsday machine in place.

The limited use of nuclear weapons has remained an official center point of Russian military strategy since a policy of nuclear "de-escalation" was officially adopted by Putin in 2000.

De-escalation is "the idea that, if Russia were faced with a large-scale conventional attack that exceeded its capacity for defense, it might respond with a limited nuclear strike," Nikolai N. Sokov, a senior fellow at the Vienna Center for Disarmament and Non-Proliferation, wrote for the Bulletin of the Atomic Scientists.

This is a military strategy that envisions that "the threat of a limited nuclear strike that would force an opponent to accept a return to the status quo ante," Sokov notes. "Such a threat is envisioned as deterring the United States and its allies from involvement in conflicts in which Russia has an important stake, and in this sense is essentially defensive."

Although de-escalation is intended to be a defensive strategy, Russia has included simulations of nuclear strikes in all large-scale military exercises since 2000 to make the threat credible. This might be one of the reasons Russia is staging a massive strategic nuclear exercise this month, amid intensifying conflict in eastern Ukraine.

According to experts, de-escalation is a principal aspect of Russian military doctrine due to the country's relative weakness in terms of conventional military strength, compared to the NATO states. The reliance on the threat or possibility of nuclear counter-measures is the only way that Russia can stand up to the combined strength of the U.S. and NATO in the event of all-out war.

"Russia is acutely aware of its conventional weakness," Nichols writes at The National Interest. "[E]ven as they torment Ukraine right under NATO’s nose, the Russians know that they have no chance against NATO without nuclear weapons."

However, as Nichols notes, Moscow knows that its reliance on nuclear weapons is an unsustainable crutch, and that Russia's conventional forces are still sorely in need of modernization.



Below is a video from National Geographic on the establishment of the Soviet Dead Hand system: