Jeffrey LewisNuclear Weapons Transparency

Greetings from Wilton Park.

I am sitting here next to the Big Swede himself, very occasional contributor Andreas Persbo. He says tjenare.

Did you know the UK nearly let the Soviets see inside a Blue Danube nuclear warhead in 1961?  Talk about transparency!

The context was test ban negotiations between the United States, United KIngdom and Soviet Union in 1960. It’s an interesting little story.

Black Boxed Bombs

The United States wanted to negotiate a test ban that permitted both “peaceful nuclear explosions,” as well as a limited number of additional nuclear explosions to better understand the seismicity of underground nuclear explosions under the “seismic improvement program”.

Not surprisingly, the Soviets believed this would allow the United States to develop and stockpile new nuclear weapons.

True to the American character, Washington earnestly proposed a totally unworkable pool of US, UK, and Soviet nuclear weapons that would be “black boxed” — set aside in advance of the treaty under some impartial authority that would make them available for limited purposes. The US contribution would most likely have been some number of Mark VII warheads.  The Soviets said they weren’t interested in contributing to such a pool, but would insist on the blueprints for any US or UK warheads in the pool and the right to look inside to confirm the warheads matched the designs.

The United States balked at that idea, although the Eisenhower Administration appears to have briefly considered letting the Soviets look inside a gun-type device.  If you are interested in more detail, I recommend William E. Ogle, An Account of the Return to Nuclear Weapons Testing by the United States After the Test Moratorium 1958-1961 pp.170-177 and The Making of the Limited Test Ban Treaty, 1958-1963,William Burr and Hector L. Montford, editors, August 8, 2003.

Blue Danube

The Washington had a better idea: Maybe the Soviets would be satisfied with seeing a British nuclear weapon?

US officials were not willing to give up on additional explosions to calibrate seismic monitoring capabilities, but believed Congress would never allow the Soviets to peek inside a US nuclear weapon. Some US officials thought Congress might be persuaded if the US had reciprocal access to a Soviet weapon, but Moscow wasn’t interested in contributing to the pool.

Hence, the idea of using British weapons. The UK was prepared to make available a British weapon for the pool, allowing the Soviets to inspect the warheads. Is it too soon to make a Klaus Fuchs joke?

The story is recounted in some detail in British Nuclear Weapons and the Test Ban 1954–1973 by John Walker.  (See especially pp 145-157.)  Since we’re operating under the Chatham House Rule, I couldn’t possibly confirm that it was John Walker who mentioned it in the meeting. Walker writes:

The MOD told the Foreign Office on 22 February 1961, shortly before the Foreign Office Minister of State went to Washington to discuss testing issues, that in the last resort, after the US had proved itself quite unable to overcome its present difficulties over the safeguards issue, and if as a result the Geneva talks were threatened with collapse, it would favour offering a UK device as a means of breaking this impasse.  However, this offer would be limited to the UK’s first generation nuclear weapon, Blue Danube, while safeguarding the security of ancillary equipment.

Although Blue Danube was still in service, it was a simple and extremely large device that would soon be retired.

As it turns out, the Soviet Union broke the moratorium in August 1961. With that, there was no longer to any requirement to let the Soviets peek inside a US or UK nuclear weapon. The three parties eventually negotiated a limited test ban that prohibited nuclear explosions in the atmosphere, outer space and under water — but not underground.  That would have to wait until the 1996 Comprehensive Nuclear Test Ban Treaty, which has yet to enter-into-force.

What is interesting to me, though, is that the UK almost let the Soviets do it — and at the height of the Cold War, no less.  That is worth remembering when people get the vapors about the UK-Norway Initiative or other efforts to verify warhead dismantlement.


Gessner “Gave Them All of It” Anyway

Speaking of Klaus Fuchs — at the same time the United States was reluctant to disclose design information on the Mark VII to the Soviet Union, a US army nuclear weapons technician was doing quite a bit to, er, enhance the transparency of US nuclear weapons designs including the Mark VII.

George John Gessner, an Army private, completed an 18 week course in the Army Ordnance Nuclear Weapons School at Sandia in September 1960 to qualify as a nuclear weapons maintenance specialist. “As part of the Sandia course [Gessner] was instructed on the internal construction and firing system of the Mark VII nuclear weapon, and the design and operation of the 280-millimeter and 8-inch gun-type nuclear weapons,” the 10th Court of Appeals wrote, “the information he eventually transmitted to the Russians.”

It seems Gessner became underwent a religious conversion and became quite worried about nuclear war.  He related a plan to his fellow soldiers to plant a nuclear weapon at the United Nations to hold world leaders hostage until they agreed to some sort of international peace treaty.  He eventually went  AWOL in December 1960, traveling to Mexico City where he visited the Soviet Embassy and disclosed design information about three US nuclear weapons.  He eventually made his way to Panama, where he was arrested.

Gessner confessed after an Army Chaplain urged him to “come clean with the Lord.”  Gessner blurted out “I gave them all. I gave them all of it.”  Apparently, Gessner forgot that while he might have given his soul to the lord, his ass still belonged to the US Army. Gessner was convicted and sentenced to life imprisonment, but was released in 1968 after a court concluded his confession had been coerced.   As best I can tell he died in Texas in 1974.

Strangely, no one in any of the US or UK documents mentions that many designs they wanted to keep secret had been, at least in part, compromised by espionage.


  1. Simon Gatehead (History)

    Interesting! And liked the nod to Full Metal Jacket. Forgetting your ass belongs to the corps is reason enough for punishment.

  2. Chris Kessler (History)

    sounds like no consideration or requirement for recprcity. assume there is some context behind that failure to require equivalent access to a Soviet weapon, but what was the hook.

    • Jeffrey (History)

      The Eisenhower Administration, so far as I can tell, thought reciprocity might tempt Congress, but the Russians made clear that they would not contribute to the pool because they regarded the seismic experiments as wasteful.

    • Pavel (History)

      Funny that they ended up making 39 of those seismic experiments.

  3. Nukeman (History)

    No should forget the works of Annette Schaper (Peace Research Institute Frankfurt) when it comes to talking and reading about verification. She has written quite a bit in the field and while scientific at times, it is well worth the trouble to read what she has to say.

  4. rwendland (History)

    The Blue Danube Mk 1 was certainly a simple Pu weapon (10 kt). But the Blue Danube Mk 2 (or “Improved Mk.1 Bomb”) at 16 kt was most probably a less simple composite core weapon.

    I wonder which version was pencilled in to maybe be shown to the Soviets? I don’t know if any Mk 1s were still around in 1961, so there might not have been any choice.

    Source of this info is Brian Burnell’s wonderful nuclear weapons history website. There is some discussion of the Blue Danube at and below:

    • Jeffrey (History)

      I believe they UK intended to “remake” a warhead — ie manufacture at considerable cost a new weapon to the old design. The weapon required some redesign to achieve the specific yield (or perhaps yields) of the seismic research program. There was some question of technical risk.

    • rwendland (History)


      The original Blue Danube Mk 1 had a near 10% chance of fizzling (or Pre-detonation as the Brits called it then) using the initial military Pu grade output of the Windscale piles. I guess that would be considered unacceptable for an international seismic research program, so part of the “considerable cost a new weapon” might well be on supergrade Pu to reduce the fizzle risk.

      NB if the initial plan 30 kt core for the Blue Danube had been built, it was calculated to have an 18% Pre-detonation risk. Part of the reason for reducing to 10 kt was reducing this risk, as well as using limited Pu production more effectively. Also why UK got into composite core ASAP. Helps indicate why DPRK went for small Pu weapons, and even then had a fizzle.

  5. Bradley Laing (History)

    Gessner left Fort Bliss that night, hitchhiked across the border to Juarez, Mexico and caught a bus to Mexico City. He took with him a small canvas bag containing five unclassified training manuals, a few clothes and personal items. The appellant arrived on December 9 in Mexico City and went the following morning to the Russian Embassy. He here used his unclassified training manuals and his Sandia diploma as certificates of introduction

  6. Bradley Laing (History)

    “Reminded of this Gessner laughed.”

    Associated Press Article from 1966

  7. A Total Stranger (History)

    Thanks for an interesting look at the history of nuclear test bans! The so-called black box bomb pool is an interesting idea and one can see the attraction it must have had for some (not allowing new weapons to be tested etc.) But “wooden bomb” might have been a better description of the bombs stored in it. Im reminded of something Michael Dobbs says in his excellent book, Five Minutes to Midnight, that Soviet bombs required strict control of temperature and humidity. Of course, its impossible to know how strict this would actually have to be, but if the pool had to have such strict environmental controls, it might give away some important design information. Perhaps considerations like this influenced the Soviets?