The world held its breath on October 14, 1962, when US fears were confirmed. The Soviet Union had stationed medium-range nuclear missiles in Cuba, a mere 200 kilometers (124 miles) from the US coastline of Florida. The Soviets therefore not only threatened the US military base Guantanamo in Cuba, but also directly the populous east coast of the United States.

When US President John F. Kennedy demanded the unconditional withdrawal of the missiles in a television address on October 22, the strategic air force forces were already in "defense condition 2" - just one step below the beginning of combat operations. The world had probably never been so close to a nuclear war before than at that point in time.

Experts say the fact that Soviet leader Nikita Khrushchev caved in on October 28 and the Cuban crisis didn't end in a nuclear disaster was mainly a result of the nuclear stalemate between the US and the USSR, the two decisive powers in the world order at the time. Neither of the two superpowers could be sure that the opponent wouldn't have the capability to undertake a second strike after a nuclear attack. The decades of nuclear armament therefore had a stabilizing effect.

Nuclear powers and aggressive rhetoric

This "balance of terror" has not existed again since the end of the Cold War, says Reinhard Meier-Walser, honorary professor for international politics at the University of Regensburg.

"Today, we have the problem of horizontal proliferation," Meier-Walser told DW. "This means that the major nuclear powers are disarming, but new nuclear powers are coming into play and we don't know if they can definitely be deterred." In addition to the "official" nuclear powers US, Russia, Britain, France and China, not only Israel and India, but also the politically unstable Pakistan and the autocratic North Korea have "the bomb."

North Korea's Vice Foreign Minister Pak Kil Yon threatened in a speech before the UN General Assembly last month that a mere "spark" could set off a nuclear war on the Korean peninsula. And there appears to be no way to keep Iran - which has signed the 1968 non-proliferation treaty as opposed to the other four "unofficial" nuclear powers - from pursuing its controversial nuclear program, or its aggressive rhetoric toward Israel. Does the logic of deterrence even work anymore today?

Arms race in the Middle East

Nuclear weapons always contain an incalculable risk. You can never know for certain just how rational a nuclear-armed country will behave, said Annette Schaper, an expert on security and governance policies at the Peace Research Institute Frankfurt. However, Schaper said she considered it unlikely that North Korea or Iran - should it one day possess nuclear weapons - would wage a nuclear first strike, as they would have to expect counterstrikes.

Both countries are cases of undemocratic, internationally isolated nations. In addition, North Korea's economy is in a dire state.

"In such a situation, isolated countries often begin to outwardly appear aggressive in order to exploit the outward threat," Schaper said. They therefore hope to be able to better push through their interests vis-à-vis other states. In addition, the common enemy from the outside would hopefully have a stabilizing effect domestically.

In the case of Iran, its nuclear program is all about striving for power, prestige and most of all the regional dominance. Schaper and other experts say the danger is that countries such as Saudi Arabia who feel threatened by a nuclear armed Iran could trigger an arms race in the already unstable region.

Already, Iran is surrounded by five nuclear powers. Meier-Walser said deterrence could therefore be the motive for Iran's nuclear ambitions. He said many countries feared that Iran could one day pass on nuclear equipment or know-how to militant Islamist organizations such as Hezbollah or Hamas, which Iran openly supports.

Pakistan and India not on a par

Nuclear weapons in the hands of terrorists is also a nightmare scenario in the case of Pakistan. The network around the Pakistani engineer Abdul Qadeer Khan, considered the architect of Pakistan's nuclear weapons program, has passed on nuclear technology and know-how for years.

"Pakistan's behavior has truly been catastrophic," Schaper said. "All secret enrichment facilities in Iran, previously in Iraq and even in Libya originate from the Pakistani network." Pakistan itself has also been arming itself. Since its foundation in 1947, it has been at odds with neighboring India. The arms race between the two countries is somewhat reminiscent of the East-West conflict during the Cold War.

But Schaper also points out differences. India and Pakistan are direct neighbors and have a territorial conflict over Kashmir. In addition, the relationship between the economically growing and internationally respected India and the unstable Pakistan are very asymmetric. Meier-Walser also said there were differences today to the arms race during the Cold War.

"The functioning of deterrence was tied to an entirely different number of conditions," he said. "Today, these conditions no longer exist, or at least not in their entirety, for example major conventional capabilities." The danger exists that in a crisis countries such as Pakistan or Iran only have the option between caving in or employing nuclear weapons, since their conventional weapons are inadequate to beat their opponent.

For Meier-Walser, the solution can therefore only be found in the disarmament of all countries in the medium-term. Schaper sees the situation similarly.

"During the Cuban missile crisis, no one obviously went berserk. That saved the world," Schaper said. "But likewise, someone could be sitting at the button who we don't know and could react differently."