New modifications to the half-a-century old iconic US nuclear bomb might jeopardize the global strategic balance, as the weapon’s characteristics might make it too tempting to not actually bring it to bear, politicians and military experts are warning.

The US has announced the successful flight test of its B61-12 gravity nuclear bombs in Nevada. The bomb did not have a warhead, as the goal was to test its flight capabilities as well as the plane’s “capability to deliver the weapon,” according to the US National Nuclear Security Administration (NNSA). It was the second successful test of the new munition this year.

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Old bomb's new life

The B61 is the primary thermonuclear gravity bomb in the US nuclear weapons stockpile adopted in the Cold War era. The munition was designed in 1963 and entered service in 1968, remaining in service for some 50 years. The life-span of each bomb is 20 years, after which it needs refurbishing.

The 3,4,7 and 11 modifications remain in active service, while a number of modification 10 bombs are in an inactive stockpile. The bombs have varying yields, ranging from small to intermediate (between 0.3 and 340 kilotons), allowing it to be used both as a tactical and strategic weapon.

The stated goal of the B61-12's development is to extend its life span, according to an official factsheet issued by the NNSA.

“The aging weapon system requires a life extension to continue deterring potential adversaries and reassuring our allies and partners of our security commitments to them,” the factsheet reads.

The B61-12 modification, however, appears to be much more than a simple refurbishment of aging nuclear munitions. The new weapon has become the first guided US nuclear gravity bomb after being fitted with a new tail kit and internal guidance system.

The guidance kit has been delivered by Boeing, based on its work with the Joint Direct Attack Munition (JDAM) – the kit to transform old conventional aerial free fall bombs into guided ones.

The series of test flights of the B61-12 tail assembly was launched by the NNSA in July 2015. The bomb demonstrated an accuracy within 30 meters, according to Federation of American Scientists (FAS).

While little is publicly known about the accuracy of the free fall nuclear munitions, its normal result is about 116 meters from target, according to information released to FAS by the military in the late 1990s under the Freedom of Information Act.

High precision allows the new modification to feature a less powerful warhead, yielding from 0.3 to 50 kilotons.

Moreover, the bomb has demonstrated high earth-penetrating capabilities, making it a sort of nuclear bunker-buster bomb capable of striking deep underground structures.

As a significant part of energy during an aerial nuclear blast bounces off the ground, the earth-penetrating capabilities allow the B61-12 to strike underground facilities while having a much lower yield than previous modifications.

The first production unit is expected to be delivered in 2020 and by the mid 2020s, production of the B61-12s should be completed.

“The completion of the B61-12 LEP [Life Extension Program] will result in a 53 percent reduction in the number of gravity weapons fielded and an 87 percent reduction in the total amount of nuclear material used by air-delivered gravity weapons, while continuing to meet military requirements,” the NNSA factsheet further reads.

Lowering threshold of nuclear weapon usage

The new B61 modification's paradox is that its increased precision and lowered nuclear yield could actually lower the threshold to use such weapons.

Russia has repeatedly warned that the development of the lower-yield nuclear weapons would destabilize the global security situation and make it “more tempting” to actually use it.

“The feature of the new modification, according to the American military itself, that it will be “more ethical” and “more usable,” since it’s more accurate and allegedly less catastrophic for civilian population in case of usage at large areas,” the director of Russia’s foreign ministry's Department for Non-Proliferation and Arms Control Mikhail Ulyanov told TASS.

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Some top US officials have advocated the development of the new low-yield bomb, claiming it would “minimize the civilian casualties,” ignoring, however, the well-known long-term effects of radioactive contamination and collateral damage.

“Though not everyone agrees, I think it’s the right way to proceed,” The New York Times cited the former US undersecretary of defense James N. Miller as saying. “Minimizing civilian casualties if deterrence fails is both a more credible and a more ethical approach.”

Russia, however, believes that it will only make the use of nuclear weapons a more viable option in the military's strategy.

“We can draw a conclusion, that adopting such bombs can effectively lower the threshold for nuclear weapons usage. We believe that’s the main negative effect of the ongoing modernization,” Ulyanov said.

The low-yield modification of the B61 bomb might water down the nuclear nature of the munition so that it would be perceived as just another bomb to use, retired army Colonel and military analyst Victor Litovkin warned.

“This is a very serious threat, as it lowers the threshold of nuclear weapons use. They can effectively say, ‘It’s not nukes that we use, we use ordinary, explosive bombs’. So these bombs, after the US completes the modification, can be used in military action, say, in the Middle East or North Africa,” Litovkin told RT.

Center for Strategic Studies Director Ivan Konovalov believes, “There’s a threat, that, for example, the Supreme commander-in-chief of the US Armed Forces Donald Trump may decide that since the bomb is guided and the blast won’t be that powerful, it can be used. That’s the most dangerous part of the situation – feeling that it’s a high-precision bomb might give the president a moral right to use it. The consequences would be disastrous.”

‘Limited’ nuclear war for Europe?

The new modification of the bomb will most likely end up in the US nuclear stockpiles in Europe, as according to expert estimates, some 150-200 B61-3 and B61-4 bombs are stored at six bases in five countries: Belgium, Germany, Italy, the Netherlands, and Turkey.

“The tests of the bomb’s new modification indicate that the US continue with the accelerated program of refurbishing its tactical nuclear stockpile in Europe, as well as that both Washington and Brussels consider the scenario of a limited nuclear war in Europe,” Igor Korotchenko, military expert and editor-in-chief of the National Defense magazine told RIA Novosti.

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The B61-12 is destined to become the main tactical nuclear munition in case of a hypothetic military conflict between NATO and Russia, Korotchenko added.

“In the course of the regularly held drills, including those in the Baltic Sea, the air forces of NATO countries have repeatedly performed combat training tasks which included tactical nuclear strikes on targets in the north-west of our country,” Korotchenko said.

The refurbishing of the US nuclear stockpile might reignite the decades-long debate whether the weapons protect the countries housing the weapons or make it a target for an atomic strike in case of a full-blown conflict.

Following the withdrawal of US nukes from the UK, which has its own nuclear weapons, then-German foreign minister Frank-Walter Steinmeier said the B61 stockpile in Germany was a “military obsolete” and urged the US to remove the weapons.

In 2013, the former Dutch prime minister, Ruud Lubbers, called the nukes stored in his country “silly things” belonging to the Cold War era.

“I would never have thought those silly things would still be there in 2013. I think they are an absolutely pointless part of a tradition in military thinking,” Lubbers told a National Geographic television documentary.

Concerns have also been raised over security at some of the facilities housing the bombs. In the late 2000s, an anti-war group calling themselves ‘Bombspotters,’ repeatedly infiltrated the Belgian air base of Kleine Brogel where the nuclear weapons are believed to be stored. The activists wandered the facility for hours before being detained by the Belgian military.

Does the B61-12 violate the Non-Proliferation Treaty?

The new modifications to the B61 bomb might violate the US' own internal nuclear guidelines, FAS warned back in 2014.

Former US Air Force Chief-of-Staff, General Norton Schwartz, confirmed to FAS that the new modification would make the weapon “better” and result in a new “target set.” Schwartz’s statement directly contradicts the 2010 Nuclear Posture Review.

“The United States will not develop new nuclear warheads. Life Extension Programs (LEPs) will use only nuclear components based on previously tested designs, and will not support new military missions or provide for new military capabilities,” the 2010 Nuclear Posture Review document reads.

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Given the new capabilities and intended use, the B61-12 bomb might also violate the Non-Proliferation Treaty (NPT), Mikhail Ulyanov believes.

“The new modification B61-12 bombs are also aimed at deployment at the territories of several NATO countries in Europe for usage in the framework of the so called joint nuclear missions, involving pilots from non-nuclear NATO member-states. According to our evaluations it contradicts the NPT obligations,” Ulyanov told TASS.

The ongoing development of the B61-12 bomb modifications, however, is only the tip of the iceberg, as the US systematically violates the NPT on a much larger scale, Viktor Litovkin believes.

“Americans keep some 200 free fall atomic bombs at their storages in Europe: in Italy, Germany, the Netherlands, Belgium and Turkey. These bombs are used to teach the military pilots of those countries that don’t have nuclear weapons, how to use these bombs, and the planes used by these countries are equipped with devices to use these bombs,” Litovkin told RT.

“I won’t even get started on the fact that teaching the pilots from the countries that don’t have nukes how to use the nuclear bombs is a most violent breach of the non-proliferation treaty. Another breach is the creation of the NATO group on nuclear planning which consists of 29 states, including the countries that don’t possess nuclear weapons,” he added.