Threats by Vladimir Putin during the invasion of Ukraine have put nuclear weapons — thought to be a Cold War relic — back on the map. How does deterrence work? And what kind of protection does the European Union have?
"Our country also has various means of destruction, and, in some cases, they are more modern than those of NATO countries," President Vladimir Putin told Russians on Wednesday. "If the territorial integrity of our country is threatened, we will, of course, use all means at our disposal to protect Russia and our people," he said.
"This is not a bluff," Putin added. "And those who try to blackmail us with nuclear weapons should know that the weather vane can turn and point at them."
The words are not difficult to parse. "Since the start of the war, we have repeatedly heard such threats, which can be interpreted as a threat to use nuclear weapons," retired Bundeswehr Colonel Wolfgang Richter told DW.
Putin calls for 'partial military mobilization'
"The idea behind this is probably a message to Western states: If you interfere in the war or attack Russian territory, then a nuclear strike becomes more likely," Richter said.
Richter, who is now a senior research associate for international security with the German Institute for International and Security Affairs (SWP), said Russia's own doctrine envisaged only two cases for the use of nuclear weapons. "First, if Russia itself is attacked by nuclear weapons or other weapons of mass destruction," he said. "And, second, when the existence and survival of the Russian state is at stake."
There is no basis in international law for claiming defense should nuclear weapons be deployed to defend Russian-occupied territories within Ukraine, Richter said, even those that the Kremlin may claim to have annexed.
Psychology of deterrence
Former NATO Deputy Secretary-General Rose Gottemoller is less optimistic. In an interview with the BBC she described the Russians as unpredictable. "And in a way that could even involve the use of weapons of mass destruction," Gottemoeller said.
With more than 6,300 warheads, Russia has the world's largest nuclear arsenal. Within NATO, the United States has the largest nuclear force, with about 5,800 nuclear warheads. France is said to have almost 300 warheads, and the UK allegedly has about 215. Exact figures are not available as the nations in question keep a lot of information under wraps in connection with their nuclear programs.
Without the US's nuclear umbrella, countries in Europe could not prevent an atomic attack militarily. The "umbrella" is based on the assumption that an adversary would not dare to attack NATO countries with nuclear weapons because that aggressor would have to expect a counterattack.
NATO's nuclear powers pursue different types of deterrence. France and Britain rely on a so-called minimum deterrent. They do not assume an exchange of nuclear strikes over several days, they believe the ability to retaliate or to stop the opponent with a "final warning shot" (France) to be sufficient.
US military planners envisage, at least theoretically, the possibility of "limited nuclear war" and accordingly keep weapons on hand with reduced explosive impact.
From a legal point of view, almost any use of a nuclear weapon would violate international humanitarian law. Theoretically, conceivable exceptions include a limited nuclear attack on a warship at sea.
The German contribution to deterrence
Germany's contribution to Europe's nuclear deterrence involves Tornado fighter jets stationed at Büchel air base in the state of Rhineland-Palatinate. In an emergency, the jets, with German crews, would fly US nuclear weapons to the target. At least once a year, Bundeswehr pilots train dropping US nuclear bomb dummies.
The Netherlands, Belgium, and Italy also participate in NATO's nuclear-sharing arrangements. Between 100 and 150 comparatively imprecise nuclear gravity bombs certified for Tornado aircraft are reportedly currently stored in Europe.
"The bombs are a relic of a bygone era whose military significance today is minor," says Peter Rudolf, a political scientist with SWP. In order to use them, the enemy's air defenses would first have to be eliminated, which would require a major war.
Chancellor Olaf Scholz says Germany's contribution to nuclear deterrence is not up for discussion — even if the nuclear-sharing concept has quite a few critics in the governing coalition. Defense Minister Christine Lambrecht announced on Monday that Germany will replace some of its aging Tornado bomber jets with US-made F-35 fighter jets capable of carrying nuclear weapons.
Still regarded as an important political symbol today, nuclear-sharing had far greater significance for Germany during the Cold War than it does today. In the days of the Warsaw Pact, Germany would have been situated at the heart of the battle in the event of an armed conflict with NATO. Nuclear sharing opened up the possibility for the German government in Bonn to exert at least limited influence on the alliance's nuclear strategy.
Who decides on the use of nuclear arms?
The US president would be the person who decides whether the United States uses nuclear weapons stored in Germany, Italy, Belgium and the Netherlands. He or she would authorize the release of the bombs, and the country where they are deployed would have to agree to the bombs being dropped by its own fighter jets. Before such a deployment, the other NATO allies would presumably consult in the North Atlantic Council (NAC), NATO's principal political decision-making body.
The deployment of France's nuclear force is also decided solely by the country's president, just as the UK prime minister makes the decision for the United Kingdom. The three decision-making centers for nuclear weapons are considered an element of deterrence, as they make it difficult for an opponent to calculate how NATO would react in the event of an attack.
Nuclear weapons in the Ukraine war
Russian military doctrine is no stranger to the use of tactical nuclear weapons on the battlefield. Russia possesses such weapons, as does the US.
"First and foremost, the Russian threats have a political function," Rudolf said. "It is a message to the US not to interfere in Ukraine beyond a certain limit."
Since the annexation of Crimea by Russia in 2014, Putin has repeatedly threatened to use nuclear weapons. This may mean so-called tactical nuclear weapons with relatively low explosive power. This could be scaled down so that a nuclear strike would unleash about 1/50 of the explosive power of a bomb that destroyed Hiroshima.
But Colonel Richter doubts that there will ultimately be a nuclear strike. "If Russia were to break the nuclear taboo that has existed since 1945, the country would also be isolated and ostracized throughout the world. Putin would lose all allies, including China. This would have incalculable consequences for the political, economic, and social survival of the Russian Federation."
Richter, therefore, considers a nuclear war with NATO rather unlikely. "Russia can't win that, after all, but it would lead to mutual destruction. I think that much residual rationality is certainly still there in the Kremlin."
And perhaps Vladimir Putin also remembers an unequivocal statement by the US president. In a television interview with CBS, Joe Biden forcefully warned Putin against using nuclear or chemical weapons. "Don't do it!" Biden said. "It would change the face of war like nothing else since World War II."
This article was originally written in German. It is an updated version of an article published earlier this year.
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