He project Islero: The Spanish dream of developing the atomic bomb

During the 20th century, the development of nuclear weapons became a determining factor in shaping the contemporary international order. In particular, during the Cold War, access to nuclear technology represented a core topic national power, marking the position of states in the international system. The weapons degree program granted significant deterrent power to those states that managed to incorporate these capabilities into their defense strategies.

In this context, Spain, in a plenary session of the Executive Council Franco regime, explored the possibility of developing its own nuclear weapons program, known as project Islero. Although the project never materialized, its existence had crucial implications for Spain's defense policy and its insertion in the international arena. The decision to explore this option in such a convulsive period, and in addition to being a partially secret project , offers a unique window to understand Spain's strategic ambitions during the Cold War and its relationship with the great nuclear powers.

This analysis explores the historical context of the project[1], the motivations that drove this initiative, the internal and external dynamics that influenced its development, as well as the reasons that led to its final withdrawal It aims to assess the impact that the project had on Spain's defense policy and its international relations.

Historical Context: Isolated Spain at the beginning of the Cold War

After World War II, Franco's Spain was marginalized on the international scene due to its ideological proximity to the fascist regimes of Germany and Italy. Its alignment with Adolf Hitler and Benito Mussolini led to a UN resolution in 1946 recommending the withdrawal of ambassadors and vetoing Spain's membership in any international organization. This exclusion, added to the internal devastation caused by the Civil War, deepened the country's diplomatic and economic isolation.

In Europe, the Franco regime found itself without significant allies. During the post-war period, Spain only had the support of Peronist Argentina and Salazar's Portugal. However, in the context of the Cold War, geopolitical dynamics changed dramatically. The rivalry between the United States and the Soviet Union transformed the perception of Spain in the Western bloc. Two factors were decisive in this shift: Franco's avowed anti-communism and the country's strategic position in the Iberian Peninsula and the Mediterranean. Although the United States had excluded Spain from the Marshall Plan after the war, with the rise of the confrontation between the blocs, Washington recognized the convenience of Spain as an ally in the containment of communism.

A turning point in the international rehabilitation of Spain was the visit of the visit U.S. President Dwight D. Eisenhower in 1953. That same year, the Madrid Accords were signed, which established economic cooperation, technical attendance and mutual defense between the two countries. Thanks to these agreements, Spain received financial support and allowed the installation of U.S. military instructions in its territory -Rota, Morón, Zaragoza and Torrejón-, consolidating itself as a core topic strategic platform for NATO in its deployment against the USSR. In addition, the signature a new Concordat with the Vatican gave the Franco regime a double international recognition: both in the political-military and religious spheres.

The reinsertion process continued in 1955, when the UN accepted Spain's entry into the organization, which represented a formal recognition of its legitimacy in the international order. At the same time, the Organization for European Economic Cooperation (OEEC) and the International Monetary Fund (IMF) supported its economic stabilization plan, facilitating its integration into Western economic dynamics.

In the same year, Eisenhower delivered his speech "Atoms for Peace" to the UN General Assembly, where he stressed the need to control nuclear development and encourage its peaceful use. This speech marked the beginning of an international policy in which the United States promoted civil nuclear attendance , while reinforcing mechanisms to prevent the proliferation of atomic weapons. For Spain, access to this emerging technology represented an opportunity both in terms of energy development and an eventual deterrent capability in the new global scenario. Thus, Spain began to explore the possibility of developing its own nuclear capability.

In a world where the possession of nuclear weapons conferred power and prestige, the Franco regime perceived nuclear technology not only as a symbol of sovereignty, but also as a means to strengthen its security and international influence. Surrounded by nuclear powers and still seeking to consolidate its position in the Western bloc, Spain began to seriously consider joining the small club of nuclear-capable states.

Motivations: From national security to international prestige.

The development of nuclear technology in Spain began in 1948 with the creation of the board of Atomic Research, established by a group of scientists and military personnel in the laboratory and research workshop of the General Staff of the Navy. This organization, initially focused on military research , had as its main objectives the study of uranium deposits in the country, the training of scientists and technicians specialized in nuclear physics and atomic engineering, as well as the development of uranium extraction and metallurgy techniques. Later, in 1951, this organism gave way to the creation of the Nuclear Energy board (JEN) by means of the Decree Law of October 22nd, which set the instructions for the beginning of the research and development of atomic energy in Spain.

The interest in developing a Spanish atomic bomb arose mainly for three core topic reasons. First, Morocco's independence in 1956 led to a deterioration in bilateral relations, which generated concern among Spain's top military commanders, led by Franco and Carrero Blanco. The concern was that Morocco might attack Spanish territories in North Africa, which led Spanish leaders to contemplate the atomic bomb as a means of reinforcing the country's security and deterring possible aggression, given that the United States had already warned that it would not intervene in the event of a conflict.

Secondly, the Ifni crisis, which took place between 1957 and 1958, accentuated the need to dissuade Morocco from attacking Spanish territories in Africa. This conflict, which involved Morocco in its attempt to recover the Ifni region, demonstrated Spain's vulnerability in its presence on the African continent. Franco, aware of the importance of a deterrent strategy, saw the atomic bomb as a crucial tool to strengthen Spain's position and prevent future attacks.

Third, in addition to the national security factors mentioned above, the atomic bomb represented a crucial tool for improving Spain's international position. In the context of the Cold War, the nuclear powers dominated the global scene, and Spain pushed for the development of its nuclear capability, mainly through the creation of the JEN, as part of its strategy to modernize its energy and technology industry. Possessing nuclear weapons would not only enhance its strategic position in Europe, but also allow it to have greater influence in international affairs, ensuring its relevance in a world divided by blocs. 

In summary, Spain's drive towards the development of nuclear technology and the possibility of manufacturing an atomic bomb was motivated by a combination of geopolitical factors, mainly the desire to guarantee territorial security in the context of tense relations with Morocco. In addition, the atomic bomb represented for Spain a way to consolidate its position as a major power in international politics, strengthening its position in the world order and contributing to its reinsertion in the international community after years of isolation.

In this regard, Guillermo Velarde, one of the main promoters of the project, stated in an interview on Radio 5, part of Radio Nacional de España (RNE), that one of the driving forces behind his efforts to develop nuclear weapons in Spain was the conviction that countries with nuclear weapons are respected at the international level. In his own words, "with a nuclear deterrent force in Spain we would be respected by all and feared by some". This idea was crucial to understanding the impetus behind project Islero, which, although it did not materialize, was a milestone in the history of Spanish defense policy.

After fill in his training in nuclear physics in the United States, Velarde, a general in the Air Force, returned to Spain as one of the leading experts in nuclear technology, joining the JEN. It was in this context that he raised with José María Otero de Navascués, president of that institution, the possibility of Spain manufacturing its own nuclear weapons.

Velarde's proposal was received positively by the military high command and, in particular, by General Agustín Muñoz Grandes, vice-president of the government, who approved the idea and gave the approval for the start of the project. In 1963, with growing concern about Moroccan pressures on Spanish territories in Africa, Muñoz Grandes considered that a Spanish atomic bomb could serve as a deterrent against possible external threats. Thus, the Islero project was approached with the goal of providing Spain with a nuclear arsenal as a deterrent.

The development of the Spanish atomic bomb was conceived in very specific technical terms. Velarde, together with a JEN committee , determined that the most viable option was the manufacture of a plutonium bomb, given that uranium enrichment required highly complex and costly facilities. The plan for development The project 's development plan consisted of nine stages, ranging from the necessary mathematical calculations to the selection of a suitable nuclear reactor to produce the required plutonium.

The project was kept in the strictest confidence, with Otero and Velarde being the decision-makers. Velarde drafted the feasibility study for the project in less than three years, estimating that the construction of 36 plutonium atomic bombs could be completed in that time. Although Spain would not materialize the development of these weapons, the Islero project represented an ambitious attempt to position the country in the small group of States with nuclear capability in a context of growing international tension.

The project was baptized with the name Islero in reference letter to the famous bull Islero, which in 1947 caused the death of the bullfighter Manolete in the Linares place . This choice was not accidental, since it symbolized the lethal power and deterrence capacity that Spain aspired to achieve with the development of a nuclear arsenal. The name also reflected a certain sense of nationalist pride and the intention to provide the country with a strategic tool that would allow it to consolidate its sovereignty and strengthen its position on the international scene.

development: Spanish Oppenheimer and Franco's final reticence

January 17, 1966 marked a turning point in Spanish nuclear history. On that day, a U.S. Air Force B-52 strategic bomber carrying four 1.5 megaton Mark 28 thermonuclear bombs collided in plenary session of the Executive Council flight with a KC-135 tanker aircraft while performing a refueling operation over the town of Palomares, in Almería. As a result of the impact, both aircraft plunged into the void, causing the death of seven U.S. military personnel. Although two of the bombs were recovered intact, the other two hit the ground, causing a plutonium leak and triggering an extensive military operation by US forces stationed in Spain[2].

Since the 1960s, there had been a conflict in Spain between the technocrats of the regime, who advocated greater integration of the country into the Western bloc, and nationalist sectors, represented by military officers such as Muñoz Grandes, who defended a policy of self-sufficiency in defense. Fearing possible U.S. sanctions, Franco decided to fail the program in 1966, although he allowed the scientist Velarde to continue his research with limited resources.

Following the Palomares accident, the Spanish government, through the Nuclear Energy board (JEN), sent a team of experts to examine the contaminated area. Among them was the physicist Guillermo Velarde, who, while analyzing the remains of the bombs, detected an unusual substance: a polystyrene foam embedded in the rocks of the affected terrain. Although the U.S. authorities claimed that this material served only as protection to prevent contact between the bombs during flight, Velarde suspected that it played a key role in the detonation mechanism.

After months programs of study and simulations, Velarde managed to rediscover the physical principle known as the Ulam-Teller method, core topic in the activation of a thermonuclear bomb. This process is based on the use of a plutonium bomb as initiator, a deuterium-tritium vessel as fuel and an intermediate layer of polystyrene, which, when compressed by the radiation of the first explosion, generates the necessary conditions to trigger the thermonuclear reaction. This finding placed Spain in a privileged position in terms of nuclear knowledge , since until then only five countries, the United States, the Soviet Union, the United Kingdom, France and China, had managed to develop this subject of weapon.

Despite the theoretical progress achieved, the decision to materialize a military nuclear program generated intense discussion at the top of the Franco regime. While some sectors considered it strategic to develop their own nuclear arsenal, the Minister of Industry, Gregorio López Rodó, and Franco himself were reluctant. They argued that the start of a project of this caliber would compromise the country's foreign policy, exposing it to international sanctions that would affect the development of the atomic energy program for civilian purposes. Consequently, although Franco authorized the continuation of scientific research, he expressly prohibited the manufacture of the bomb.

Thus, despite having acquired the necessary knowledge for the production of thermonuclear weapons, Spain never carried out their development. The Islero project , although it advanced in theory and consolidated the country's technical capabilities in the nuclear field, was limited by political and strategic considerations, becoming a testimony of Spain's scientific potential in a context of strong geopolitical restrictions.

An expected end? The reasons behind the closure of the project

project Islero was originally intended to provide Spain with nuclear capacity. However, it was frustrated due to a series of factors that, both internationally and domestically, ended up making it unfeasible.

First, at the national level, there was a change in foreign policy. During Franco's dictatorship, the interest in developing a nuclear program for military purposes was linked to the policy of defensive independence and the desire for greater international recognition. However, with the Transition, Spanish foreign policy began to prioritize integration into multilateral organizations, such as the European Economic Community (EEC) and the North Atlantic Treaty Organization (NATO). Membership in these organizations required commitments in subject of nuclear non-proliferation.

Secondly, the assassination of Carrero Blanco, considered one of the main promoters of project Islero, produced an important political change. From the beginning, Carrero Blanco tried to negotiate a more equal relationship with the United States, proposing that, if Washington wished to continue using military instructions in Spanish territory, it should share advanced military technology. In 1973, he met with Henry Kissinger with the goal of pressuring him to obtain a cooperation agreement that would guarantee Spain's security. However, he failed to obtain a concrete commitment; the next day he was assassinated by ETA, which weakened the political leadership in favor of nuclear weapons development .

Thirdly, in the international arena, the Nuclear Non-Proliferation Treaty (NPT) was adopted. From the mid-1960s, the United States promoted a global policy to curb nuclear proliferation, which led to the negotiation of the NPT between 1965 and 1968. The signature this Treaty implied submitting nuclear facilities to inspections by the International Atomic Energy Agency (IAEA), which would have meant the interruption of the French partnership with Spain in this field. Although the treaty entered into force in 1970, Spain resisted signing it, maintaining its position until 1987.

Fourth, and related to the previous point, there was strong pressure from Jimmy Carter. In 1977, with the arrival of Carter to the US presidency, efforts were intensified to get the non-signatory countries of the NPT to adhere to the Treaty. Spain, which had not signed the NPT and was planning to install an irradiated fuel treatment plant in Soria, found itself in an awkward position. U.S. mistrust led to a tendency to reduce supplies to the Spanish nuclear plan, which could become a major obstacle to the program. In 1981, following the attempted coup d'état in Spain, the government of Leopoldo Calvo-Sotelo relented and agreed to place the country's nuclear facilities under IAEA safeguards.

Fifth, the economic and technical calculation was unsustainable. The development of a nuclear arsenal implied large-scale investments, both in infrastructure and in research and development. For the Spanish Economics at the time, which was going through structural difficulties and was in the process of opening up and integrating into international markets, these costs were unsustainable. In addition, the dependence on foreign components made it difficult to materialize the project.

Sixth, Spain used the possibility of developing nuclear weapons as a diplomatic strategy. This 'credible threat' made it possible to obtain certain concessions in the international arena without incurring the costs and political risks of actually building the bomb. However, as the international context changed and pressures increased, this strategy lost viability.

Finally, accession to the EEC and the NPT definitively closed any possibility of reactivating the project. This decision, taken under the government of Felipe Gonzalez, was linked to the will to fully integrate into the EEC, which required demonstrating a firm commitment to nuclear non-proliferation and international stability.

In conclusion, the failure of project Islero was the result of a combination of international pressures, changes in Spanish foreign policy, economic difficulties and internal divergences within the government. Eventually, Spain definitively abandoned the idea of developing nuclear weapons and opted for a policy of integration into the international system, consolidating its image as an actor committed to peace and global security.

Conclusion: Spain's Commitment to Non-Proliferation

Spain's acquisition of nuclear weapons sought by project Islero would have had profound implications, both domestically and internationally, affecting the geopolitical balance and Spain's position in international relations. However, historical evolution has demonstrated Spain's firm commitment to the nuclear non-proliferation regime, consolidating its role as a manager actor within the international system.

Spain has reaffirmed in multiple international forums, such as the multiple NPT Review Conferences, its support for this treaty as a cornerstone of the global nuclear non-proliferation and disarmament regime. Its adherence to the NPT has allowed it to strengthen its cooperation with strategic partners, such as the European Union and NATO, in addition to guaranteeing its access to nuclear technologies for peaceful purposes under IAEA standards.

In this context, Spain supports the implementation of gradual disarmament measures, such as those proposed in the 'Stepping Stones' document, and the entrance into force of the Comprehensive Nuclear Test Ban Treaty. Furthermore, its commitment to international stability is reflected in its position on the Iranian nuclear agreement and its condemnation of North Korea's provocations, advocating complete, verifiable and irreversible denuclearization. Spain also supports the IAEA's initiative to guarantee nuclear safety in Ukraine in the framework the conflict with Russia, endorsing the 'seven pillars of nuclear safety'.

In conclusion, Spain's decision not to move forward with the development of a nuclear arsenal has allowed it to consolidate its integration into the international community and its adherence to a rules-based order that prioritizes peace, stability and global security. Through its commitment to non-proliferation and nuclear disarmament, Spain reaffirms its responsibility to build a safer world free from the threat posed by nuclear weapons.