[2] The option to continue development of weapons was abandoned in 1966, and Sweden's subsequent signing of the Non-Proliferation Treaty (NPT) in 1968 began the wind-down of the program, which finally concluded in 1972.

[2] During the final phase of World War II, the Swedish Government saw value in the future of nuclear energy, especially the Allied interest in Sweden's uranium-bearing black shale deposits.

After American Ambassador Herschel Johnson brought up that question in a conversation with State Secretary for Foreign Affairs Stig Sahlin on 27 July 1945, the issue was raised at the government meeting on 2 August.

Physics-oriented defence research started in Sweden during World War II, and drew many outstanding Swedish physicists to the Military Institute of Physics (MFI) founded in 1941.

In August 1945, just a few days after the Hiroshima bombing, Sweden's Supreme Commander of the Armed Forces, Helge Jung, made a request via newly appointed research officer Torsten Schmidt that the recently founded FOA should find out what was known about those new weapons.

In 1947, AB Atomenergi (AE) was founded under initiative of the Atom Committee with the goal of building experimental reactors and developing methods to extract uranium from low-grade Swedish deposits for both civilian and military needs.

In 1954, Nils Swedlund, Supreme Commander of the Swedish Armed Forces, publicly declared that nuclear weapons were crucial for the country's national security.

Although two years earlier, Air Force Chief Bengt Nordenskiöld had already advocated for Swedish possession of nuclear weapons, his comments were understood to be personal opinion and did not stoke much debate at the time.

The alternative construction included superheating mechanism, internal reshuffling machine, and a complex process of boiling water, which ultimately complicated design and raised serious concerns.

That same year, the FOA (upon the Chief's request) undertook a detailed study of what would be needed to develop Swedish plutonium-based nuclear devices with estimates for timeframe and costs.

The FOA's chief director, Hugo Larsson, also helped to energize the debate with an interview in Dagens Eko in 1957, in which he said that Sweden had the resources to build nuclear weapons, which could be completed in 1963–1964.

[26] Among the proponents of Swedish nuclear weapons program was Dagens Nyheter's chief editor, Herbert Tingsten, and former Social Democratic Defence Minister Per Edvin Sköld.

The editor of Folket i Bild, Per Anders Fogelström, advocated against Swedish nuclear weapons in the magazine, and published a book "Instead of the Atomic Bomb" together with Social Democratic student politician, Roland Morell.

Swedlund's diaries and other documents suggest that he had limited understanding of the political game, not least within the parties, even though his own statements in 1957 contributed to the creation of nuclear weapons resistance.

[31] While the L-program was left unfunded, FOA was given a large allocation for fiscal year 1959/1960 for "increased research in atomic-, missile-, countermeasure-, and other areas" in which the S-program was relevant.

[34] Thus, Palme preferred to postpone the crucial decision for years, with the goal of avoiding a serious split in the party, as opposed to a difficult compromise necessary to satisfy the desires of both sides for the long run.

When the government brought up the issue in 1961, Erlander said that he himself now swung in the negative direction regarding the nuclear program, as compared to his views 3–4 years earlier, which he had never announced publicly.

As a result, Sweden got access to some previously classified materials, and the opportunity to import small amounts of enriched uranium and heavy water at prices lower than those from Norway.

[41] From 1959 onwards, Swedish interest in pursuing a uranium mill at Ranstad (the construction of which was decided in 1958 and scheduled to open in 1963) and a domestic supply of heavy water declined.

As a result, in 1957 the Swedish Government started to study the opportunity to set up and operate one or possibly two purely military reactors for plutonium production located in caverns.

[43] The decreased civilian interest in domestic supply of raw materials resulted in revision of plans to build nuclear weapons facilities in Sweden in 1959 and 1960.

An agreement with Western powers that would quickly come to Sweden's aid, or a purchase of a small number of nuclear weapons from the West, most likely the US, were options also considered.

[46] In 1960, while Sweden was deciding on its stance toward nuclear weapons, Swedish representatives, through their contacts with the American Department of Defence gained access to some secret information in the late 1960s.

[53] In order to prevent the elimination of nuclear striking ability by a surprise attack, the Swedish Government outlined a system where the majority of warheads would be stored divided amongst heavily defended caverns, and the rest would move between airbases.

[65] The negotiations between the Soviet Union, Great Britain, and the US in August 1962 ended in an agreement to abandon all nuclear weapons tests in the atmosphere, outer space, and underwater.

In March 1966, Undersecretary of the Defence Department Karl Frithiofson in his speech before the Royal Swedish Academy of War Sciences publicly announced that it was of no interest to Sweden to acquire nuclear weapons, which was a slight difference from the Freedom of action doctrine.

Additionally, the late Anna Lindh, Sweden's former minister for foreign affairs, took the lead in promotion of non-proliferation policy, which eventually affected the European Union's strategy to combat the proliferation of weapons of mass destruction (WMD).

[70] Karl Frithiofson in his speech in March 1966 announced that Sweden gave up its plans to acquire nuclear weapons, which in its turn put the end to the freedom of action doctrine.

As a reaction to it, the Social Democratic-led Swedish government set 1995/1996 as years to start the implementation of a phase-out plan, including the shut-down of two nuclear reactors.

Many documents on the Swedish nuclear program's development phase and most intensive periods had therefore been gradually opened to public during the 1990s, and laid the foundation for studies for such experts as Wilhelm Agrell and Thomas Jonter.