“Peace, Disarmament, Cooperation”
A Contribution to the Debate on World Peace and Security
Frederico Carvalho
23d General Assembly of the WFSW, May 9-12, 2022

“Peace cannot be kept by force.
 It can only be achieved by understanding”
Albert Einstein


According to the most recent estimate of global nuclear warhead inventories published by the Federation of American Scientists, nine countries possessed roughly 12,700 warheads as of early 2022 [1]

Approximately 90% of the total number of warheads are in possession of the USA and the Russian Federation with equivalent military stockpiles. There are at present 9 nuclear armed states. France and China come next, each of them with similar stockpiles of a few hundred useable weapons, followed by the UK, Pakistan and India with less than 200 hundred warheads each. Finally, Israel may be in possession of an estimated number of 90 weapons while North Korea probably owns no more than 20 useable warheads.

Only about 3.7 thousand, or 1 in every 3 warheads in the global inventory is counted as “deployed”. These are warheads that are mounted on launchers ― either an intercontinental missile or an operational short-range delivery system ― or are ready to be delivered by an aircraft in air to ground attacks. In this case they are guided by gravity (gravity bomb) and have none or limited guidance possibilities. Warheads stored at bomber bases are thus counted as deployed.
The number of American and Russian deployed warheads is almost the same: 17 hundred to 16 hundred respectively.

Warheads assigned to short-range delivery systems are named “non-strategic”. The so-called “tactical” or “low yield” warheads belong to this category. The B61-12 presently being tested by the American Air Force is a tactical bomb that comes in several varieties ranging from 0.5 kt to 50 kt. For comparison, the explosive yield of the bomb dropped on Hiroshima was near 14 kt of equivalent TNT. The F35 fighter jet is nuclear capable and may deliver the relatively light warheads of the B61 family. Approximately 100 B61 bombs are deployed in Europe at six bases in five countries (Belgium, Germany, Italy, Netherlands, and Turkey) [2].

“Retired” warheads (see figure) include weapons that are no longer useable as well as weapons that are intact but await dismantlement. The latter are still counted as part of the military arsenal (“military stockpile”). According to recent estimates by the Federation of American Scientists, Russia is dismantling 200-300 retired warheads per year[3]. The same source defines “Reserve/Nondeployed” warheads as warheads that are not deployed on launchers but are in storage except weapons stored at bomber bases which are considered “deployed”.

Towards the end of the years 80 of the past century the global inventory of nuclear warheads reached a peak of circa 70 thousand that is about 6 times the present number. A steep decline of the numbers of the inventory was verified since those years until the first decade of the present century. Since then the numbers of the global inventory have remained relatively stable. These is mainly due to the fact that the US and Russia are still dismantling previously retired warheads while the number of warheads in global military stockpiles is increasing once again.

One should note that the exact number and composition of nuclear weapon inventories is in general held as a close secret by the national authorities of each nuclear-armed state although there are different degrees of transparency. Publicly available information is the fruit of a considerable research effort carried out by private national and international NGO´s engaged in contributing to preserve peace and stability in our world.[4]

According to a number of reliable sources, although the total number of operational warheads appears to have stalled their numbers may be rising again. Not only the two major nuclear-armed states are engaged in extensive and expensive research and development programs that aim at improving their military nuclear capabilities but every other nuclear armed state appear to be following the same path. The programs comprehend replacement and modernization of warheads, missile and aircraft delivery systems, and nuclear weapon production facilities.

In this context one should also note the fact that, globally, the world military expenditure has been steadily rising for several years.
The Stockholm International Peace Research Institute’s press release of April 25, 2022, informs that after 7 years of consecutive growth the world military expenditure in 2021 has for the first time exceeded 2 trillion US dollars. In fact, US$2.13 trillion ― a record level attained, as the Institute points out in the press release, in the second year of the COVID 19 pandemic.


One aspect that deserves particular attention is the degree of readiness of nuclear forces in case a nuclear armed state considers the necessity of using them. The possibility that a situation arises where that necessity appears to merit consideration has I fact been present since the end of World War II although with variable degrees of seriousness.
Since the end of the so-called “cold war” both the USA and the Russian Federation appear to maintain about 900 warheads each in a state technically described as of “prompt alert” or “hair-trigger alert” which means they are kept ready to fire at a less than a 15 minutes’ notice. In both cases we are dealing here with warheads to be launched either by an ICBM or a SLBM. ICBM’s are stationed in hardened underground silo’s whilst SLBM’s launch platforms are ballistic missile submarines (SSBN). France and the UK also keep a number of warheads in alert state, although in much smaller numbers (80 and 40, respectively). The remaining five other nuclear-armed states are thought to store their warheads separate from launchers under normal circumstances.[5]
Warheads in a state of prompt alert is, alas, nothing new. Also, not new is the fact that we are dealing here with a highly risky situation that has been criticized even by many senior military and political figures. At the height of the Cold War a number of nuclear armed bombers carrying atomic and hydrogen bombs were kept aloft around the clock, i.e. at any time a number of bombers were in the air. In an operation code-named Chrome Dome (1961-68), the US had between 12 and 24 nuclear-armed B-52 bombers in the air 24 hours a day, in an attempt to deter a Soviet first-strike. The B-52s carried nuclear weapons with all the codes and procedures for arming and releasing the bombs.
This situation was extremely risky. A number of accidents occurred including the crash of a few bombers.[6] Sadly famous is the one that occurred in 1966 when two US Air Force planes collided and dropped four nuclear bombs near the village of Palomares in southern Spain. The B52 plane involved in the accident was flying the so-called “southern route”, in a loop from its base in North Carolina around the Mediterranean. Fortunately, the bombs were not armed, so there was no nuclear explosion. However, two of the bombs that fell to earth unsupported by parachutes were blown to pieces on impact, scattering highly toxic, radioactive plutonium dust [7].
Chrome Dome operation finally ended in 1968 and with it airborne nuclear alert. As far as we know no nuclear-capable heavy bombers (known as the “air leg” of the so-called “nuclear triad”) are at present in alert status. All warheads on prompt alert are strategic warheads that may be delivered either by ICBM’s or SLBM’s.

As a general consideration we may recall that for a couple of years at the highest military level of the US armed forces voices have been heard expressing the need to replace the old Minuteman III ICBM considered obsolete by a new technologically improved missile. Since such a missile does not exist as yet those who express that opinion consider the necessity of returning the existing American modern nuclear bombers to prompt alert status. Shortly the 2022 US so-called Nuclear Posture Review is due to enter in force. Mr. Biden’s revision of the previous NPR adopted in the Trump’s presidency, states that the “fundamental role” of US nuclear weapons is to deter nuclear attack, not, as previously declared, to deter both nuclear and nonnuclear attacks. This is considered by some observers as “weakening deterrence[8] So the new policy is considered “not as good as the old”. That is: Trump’s Posture. The author cited in the previous note add that, however, “it could have been worse” since (quote) “Mr. Biden has at least rejected the ill-advised calls from the far-left to declare the U.S. would never use nuclear weapons first, even in the face of the most destructive nonnuclear attacks”. What or whom is meant by “far left” is anybody’s guess.[9]No wonder ― quote again ― so many of our allies and senior officials publicly opposed taking the nuclear option completely off the table against nonnuclear threats”.


In the nuclear age, the risks of nuclear accidents are an ever-present threat although there is not a widely spread conscience of that risk.
A recent article published in the Newsletter of the British association “Scientists for Global Responsibility” under the title “The history of accidents in the UK’s nuclear weapons programme” reminds us of the many risks of nuclear conflict, but asks whether we have forgotten the dangers of simply owning the weapons.[10]

Incidents or accidents of different degree of seriousness considering their consequences have effectively occurred in every phase of what may be called the nuclear weapon life cycle, including fabrication, transport, storage, maintenance and dismantling of nuclear warheads. A recent report cited by the authors [11] compiles all the known accidents, near misses and dangerous occurrences in the 65-year history of the UK’s nuclear weapons programme, The report lists no less than 110 serious incidents and a number of other less serious events.
It is quite probable that a similar compilation in the case of the two major nuclear powers would disclose a considerably larger number of dangerous events.
When warheads and the respective launching vectors are kept on “hair-trigger” alert the consequences of a fortuitous set of circumstances may have extremely serious consequences even the launching of an all-out nuclear war. Technical failures, wrong manipulations but also malicious hacking exploiting weaknesses in a computer system or network may lead to fatal disaster.

The only sane path to follow is the total elimination of nuclear weapons in accordance with the provisions of the Treaty on the Prohibition of Nuclear Weapons adopted by the United Nations General Assembly in September 2017, effective on January 22, 2021.


We shall now discuss the role of the so-called “low-yield” or “tactical” nuclear weapons in present day international balance of forces and their consequences on the post second World War nuclear deterrence policy. What are they and what purpose they may serve?
Let us recall the words of President Ronald Reagan in his 1984 “State of the Union Address” to the American people. He said then ‟People of the Soviet Union, there is only one sane policy, for your country and mine, to preserve our civilization in this modern age: A nuclear war cannot be won and must never be fought. The only value in our two nations possessing nuclear weapons is to make sure they will never be used. But then would it not be better to do away with them entirely?”. These words, however, were said in the context of the long-standing policy of the so called “mutual assured destruction” (MAD) doctrine of military strategy and national security policy in which a full-scale use of nuclear weapons by two or more opposing sides would cause the complete annihilation of both the attacker and the defender. As recently as January this year Reagan’s understanding of the impossibility of winning a nuclear war was reaffirmed by the leaders of the five largest nuclear weapons nations – Russia, the USA, China, France and the UK [12]

Tactical weapons are short range weapons meant to be used in the battle field. They may be airborne or be delivered by intermediate and short-range missiles and artillery. Both the USA and the Russian Federation, especially the latter, have important stocks of such weapons. Both are investing heavily in the development of new and technically more performant tactical nuclear explosive devices. Russia has an estimated arsenal of about 2000 tactical weapons, all non-deployed; the USA has an estimated 100 tactical weapons deployed in Europe and a stock of about 130 non-deployed tactical warheads[13]. Modern tactical warheads come in two flavors: fixed explosive yield or variable yield to be set by the operator. This “dial-a-yield” version allows setting the amount of energy that is liberated by the explosion. The newest version of the American B61 warhead, mentioned before, may be set to release 0.3, 1.5, 10 or 50 kilotons of explosive energy [14].

Several authors have expressed the opinion that the ascent of tactical nuclear weapons as a supposedly useful component of nuclear arsenals has the potential to lead to global catastrophe ― an all-out nuclear war. In fact, a nuclear power may decide using a low-yield nuclear weapon in a limited war scenario against an adversary that is not nuclear-armed and thus effectively cross what is called the nuclear threshold, based on the assumption that there will be no retaliation in kind from another nuclear power for fear of unleashing an all-out nuclear war. After all, this is the principle of the deterrence policy. Nothing is less sure, however. Or one could say that (quote)” nuclear weapons are not just a force used to deter another state from attacking, they can also be a shield behind which one can engage in aggression.”[15]

As Dr. Philip Webber, of Scientists for Global Responsibility, points out, “the reality is that ‘nuclear deterrence’ threatens death and destruction on such an extreme scale that it is hard to imagine. This is no accident – a detonation above a city is chosen to maximize the lethal blast and fire radius.” It is appropriate to add that the “no first use” principle has not been unconditionally accepted by any of the present nine nuclear-armed states, with the exception ― for now ― of China.

A first strike even if involving only a limited number of warheads ― let us say, 100 warheads, a number that is about one third of the arsenals of India and Pakistan put together ― “would be completely disastrous for all humanity in terms of death, injury, radiation releases and widespread ecosystem impacts. Nuclear fireballs would create huge ‘firestorms’, injecting smoke high into the atmosphere sharply reducing sunlight and creating a ten-year ‘nuclear winter’. This would bring about mass starvation and societal collapse as crops failed in unseasonal frosts and darkness [16].

As has been stressed in a number of occasions, scientific workers have a duty to intervene in the struggle for peace by making their fellow citizens aware of the threats that confront all humankind.

Recently, both in the USA and in Europe, positions have been taken by scientific workers and other intellectuals, sometimes in the form of an “open letter” addressed to the scientific community and the general public, at other times in the form of a “public petition” addressed to policy makers. One of the most notable initiatives is the recent creation in the USA of the “Coalition of Physicists to Combat the Nuclear Threat”[17] that brings together physicists from an important set of US universities and is supported by the American Physical Society, which has more than 50 thousand members in the US and other countries. Quoting the words of the Doomsday Clock Commission of the Bulletin of Atomic Scientists, the Coalition warns that “the belief that the threat of nuclear war has disappeared is a mirage”, and proposes to build a network of “citizen scientists” committed to the fight against the nuclear threat. The promoters of the initiative know, as we also know, that there is a majority of members of the scientific community that, despite the seriousness of the dangers, show a tendency to maintain a passive attitude, does not value them or ignores them, and they know, the activists of the Coalition of Physicists, that the success of their efforts depends on the participation of this majority, especially the younger ones, in a struggle that belongs to everyone.

Our association, the Portuguese Organization of Scientific Workers ― OTC, affiliated for over 40 years to the World Federation of Scientific Workers, seeks to contribute to this struggle.

Frederico Carvalho
May 4, 2022


[1] https://fas.org/issues/nuclear-weapons/status-world-nuclear-forces/
[2] See reference 1. This can be considered a breach of Articles I and II of the Non-Proliferation Treaty of which the named countries are parties.
[3] According to the FAS the number is similar in what concerns de USA (300-350 per year) (https://fas.org/blogs/security/2020/12/nuclear-stockpile-denial-2020/ )
[4] “Between 2010 and 2018, the United disclosed its total stockpile size, but in 2019 the Trump administration stopped that practice. Fortunately, in 2020, the Biden administration restored nuclear transparency – a victory for nuclear accountability in a democratic country. Despite limitations, however, publicly available information, careful analysis of historical records, and occasional leaks make it possible to make best estimates about the size and composition of the national nuclear weapon stockpiles. (…) The information available for each country varies greatly, ranging from the most transparent nuclear weapons state (United States) to the opaquest (Israel). Accordingly, while the stockpile estimate for the United States is based on “real” numbers, the estimates for several of the other nuclear-armed states are highly uncertain.”
( https://fas.org/issues/nuclear-weapons/status-world-nuclear-forces/ )
Russia refuses to publicly disclose the detailed breakdown of its nuclear forces, even though it shares the information with the USA. (https://sipri.org/sites/default/files/2021-06/yb21_10_wnf_210613.pdf )
[5]Alert Status of Nuclear Weapons”, Hans H. Christensen, Federation of Atomic Scientists, April 21, 2017 (https://uploads.fas.org/2014/05/Brief2017_GWU_2s.pdf )
[6] Rebecca Grant, “The Perils of Chrome Dome”, Air Force Magazine, Aug. 1, 2011
[7] A third bomb landed softly near the Palomares village as did the two others whose parachutes failed to open. The fourth bomb sank into the waters of the Mediterranean Sea and was found intact four months later.
Almost half a century later the decontamination process of the soil apparently was still not completed. See: “Palomares bombs: Spain waits for US to finish nuclear clean-up”, Gerry Hadden, PRI’s The World, 22 October 2012 (https://www.bbc.com/news/magazine-18689132 )
[8]Biden’s Change in Nuclear Policy Weakens Deterrence”, Patty-Jane Geller, The Heritage Foundation, April 4, 2022 (https://www.heritage.org/defense/commentary/bidens-change-nuclear-policy-weakens-deterrence )
[9] See reference 8
[10] David Cullen, Peter Burt, SGR Newsletter no.46; published online: 23 April 2018 (https://www.sgr.org.uk/resources/history-accidents-uk-s-nuclear-weapons-programme#Reference )
[11] Burt P (2017). “Playing with Fire: Nuclear Weapons Accidents and Incidents in the United Kingdom”, Nuclear Information Service. (https://www.nuclearinfo.org/article/nis-reports/playing-fire-nuclear-weapons-incidents-and-accidents-united-kingdom )
[12] The White House (2022). https://www.whitehouse.gov/briefing-room/statements-releases/2022/01/03/p5-statement-on-preventing-nuclear-war-and-avoiding-arms-races/
[13] See reference 1
[14] For comparison the bomb dropped on Nagasaki in August 1945 liberated an energy equivalent to 20 kt of TNT
[15] Scott Sagan, co-director of the Center for International Security and Cooperation at Stanford University (https://www.futurity.org/putin-nuclear-weapons-threat-war-russia-2729662/ )
[16] “Has our society forgotten the extreme horror of nuclear weapons?” Philip Webber, SGR, Responsible Science blog, 3 March 2022 (https://www.sgr.org.uk/resources/has-our-society-forgotten-extreme-horror-nuclear-weapons#_edn9 )
[17] https://thebulletin.org/2020/01/physicists-mobilize-to-reduce-the-nuclear-threat-again/