For 40 years, the assassination of Sweden's prime minister, Olof Palme, has remained unsolved. Now, some are revisiting a dark possibility: not a lone gunman, but a covert network embedded deep within Swedish society – part of a secret Europe-wide effort to resist a Soviet invasion

Published in Haaretz: 40-year Mystery: Did a Secret Resistance Network Assassinate Sweden's Prime Minister? – Europe

The most shocking event in the history of modern Sweden occurred almost exactly 40 years ago. On the evening of Friday, February 28, 1986, Prime Minister Olof Palme and his wife, Lisbet, went to see a movie in central Stockholm. It was a cold winter evening in the capital. As he often did, Palme dismissed his bodyguards and the couple travelled three subway stations to the theater without a security escort. When they emerged onto the street, they met up with their 25-year-old son, Mårten, and his partner. The four bought tickets and went in.

Shortly after 11:20 P.M., while the prime minister and his wife were walking back home along a main street in the city, a man approached them from behind and fired a gun at close range. Palme was hit and collapsed on the frozen pavement. A second shot was fired immediately afterward, lightly wounding Lisbet. Bystanders attempted to help but it was in vain. Palme died on the spot. An ambulance was called and evacuated his body and his wife to a hospital, arriving less than 20 minutes after the shots were fired.

The hours that followed were dramatic. News of the murder spread in the Swedish media and overseas. The country went on high alert, and Deputy Prime Minister Ingvar Carlsson convened the cabinet. At 5 A.M. Saturday morning a press conference was held. Flags were subsequently lowered to half-mast, flowers and candles were placed at the murder site, and an atmosphere of national mourning and crisis permeated the country. At the same time, it emerged that almost every possible mistake was made in the investigation of the murder: The shooter immediately fled; police arriving at the scene failed to apprehend him. They also did not set up roadblocks or cordon off the area. Coordination between law enforcement forces at the site was poor; no situation room was established, and testimonies from eyewitnesses were neither systematically collected nor fully documented. These errors were never corrected in the intervening four decades.

In the years following the murder, what is referred to by Swedish authorities as "the largest and longest-running murder investigation in the world" was launched, but despite significant resources, it was marred by disputes and conflicts and did not lead to any definitive outcome. Many investigative directions were pursued but no one was charged. In the first year, the Kurdish PKK organization was a central focus. Later, theories involving possible actors from various countries, such as South Africa – which allegedly had both a motive and the capability for executing a political assassination abroad – were explored but did not result in indictments. Such was also the case following investigations of theories involving terrorist organizations from the Middle East and Eastern Europe.

In 1988, a local criminal named Christer Pettersson was convicted of the murder, mainly based on a controversial identification by Lisbet Palme; a year later he was acquitted on appeal due to lack of evidence. In June 2020, the Swedish prosecution announced that the investigation was closed, declaring that a man named Stig Engström was the probable suspect. Engström had allegedly been present at the scene on the night of the shooting and had been interviewed as a witness in later years, but he died in 2000 and therefore could not be prosecuted. His motive was unclear, and the evidence against him was circumstantial and unconvincing. Nevertheless, this was enough for the prosecution to close the case.

But this was not the end of the story: In December 2025, the prosecution reversed its position. In a surprising development, it announced that a renewed examination of the investigative material had concluded that there was insufficient evidence against Engström, and thus he was no longer officially considered to be the suspect. At the same time, no other names were suggested, nor was the investigation formally reopened. Thus, 40 years later, the Swedish public still does not know who killed its prime minister or why. Meanwhile, on the margins of these developments, a discussion has surfaced about another historical phenomenon, which – like the identity of the man who pulled the trigger – was heretofore unknown to the Swedish public and kept in the shadows for decades.

"Today, we know no more about the murder than we did the day after it happened," says Gunnar Wall, a journalist and author who has dedicated years to researching and writing books about the Palme assassination. "We do not know if it was a lone assassin or an organized group, we do not know the motive, how the killer escaped, whether he was Swedish or foreign, or whether he is still alive today and, if so, is he in Sweden or abroad. Given this situation, there are countless speculations and theories."

Wall, recipient of the 1998 and 2024 Guldspaden (Golden Spade) award, Sweden's most prestigious prize for investigative journalism, for books he wrote about the incident, notes that while there are those who claim to know who the murderer was, despite years of research, he himself does not.

However, Wall points to an interesting issue. The decision not to reopen the investigation late last year is strange, in his view, because about 15 years ago Sweden changed its legislation regarding statutes of limitations. Serious inquests into crimes such as murder, under the new law, are no longer closed after 25 years as was previously the case, and can remain open indefinitely. The prosecutor who last December chose not to resume the whole process justified that by saying there were no conditions for doing so – even though he admitted that he had examined only the Engström lead and not other possibilities.

When the previous prosecutor closed the case in 2020, it was possible to say that happened because he had reached a dead end – but the same cannot be said about his successor's decision, since he said he had not even attempted to evaluate materials that did not concern Engström. And yet, he seemed determined to leave the case closed nonetheless.

"The investigators of the Palme murder examined, almost until the very last moment, indications of [involvement by] a larger group that went beyond Engström alone," says Wall, who bases his claims on interviews he conducted with the investigators themselves and with additional witnesses, as well as on reviews of countless documents, reports and other materials. "Their main hypothesis was that forces within a secret Swedish network were behind the murder, and they tried to link Engström to these actors. When they failed, they abandoned the hypothesis and Engström remained the sole suspect. Five years later, because the evidence against him was weak, it all ended with no conviction and no suspect."

Suggestions about some secret entity having been behind the Palme assassination may sound like far-fetched conspiracy theories – but they are not. For decades, underground organizations called stay-behind networks existed in Sweden and many other European countries. While a direct link between the Swedish stay-behind network and Palme's assassination has not been proven, the existence of the group is an established fact. These clandestine bodies were created after World War II as a way for countries to prepare for a possible invasion and hostile occupation. Their work included drafting blueprints for underground resistance groups, maintaining contact with a government-in-exile and actively opposing an occupier.

In the early days of the Cold War, following World War II, the threat of Soviet aggression was tangible. Across Europe, secret networks were created in various countries, in order to forge connections between the military, police, intelligence services and civil society. Initially, these organizations were intended to prepare for a Soviet invasion, but over time some engaged in other activities, sometimes even conducting covert operations within their own borders, including false flag operations – designed to appear as if carried out by others to justify certain political or military reactions.

The most famous example is the Italian network and operation code named Gladio, whose existence was revealed to parliament in 1990 by Prime Minister Giulio Andreotti. Some claimed that this stay-behind network participated in domestic acts of political terrorism in the 1970s and '80s. Parliamentary inquiries looked into its operations and ties with foreign actors and intelligence bodies such as the CIA and NATO, and exposed its involvement in guerrilla training, communications networks, weapons storage and sabotage. There were also suspicions that Italy's network operatives engaged in domestic political activity, including terrorism designed to strengthen the Italian right and diminish the left. Similar underground groups have been documented in Belgium and Switzerland, and evidence of same exists in France and Germany, although without confirmation of domestic violence. There are also hypotheses about the involvement of such networks in coups and politically motivated violence in Greece and Turkey.

The investigators' hypothesis was that forces within a secret Swedish network were behind the murder, and they tried to link Engström to these actors. When they failed, they abandoned the hypothesis.

The whole phenomenon remains highly controversial and difficult to research due to the secrecy and compartmentalization surrounding it, yet there is general agreement that stay-behind networks have existed across Europe, operating without parliamentary oversight and known to only a small circle of decision-makers.

After years of rumors and official denials of such bodies existing underground in Sweden, in 2013, one of the country's major newspapers, Dagens Nyheter, published an article by Inga-Britt Ahlenius, a civil servant who worked at the Ministry of Finance, the National Audit Office and the United Nations. Based on evidence and research that had emerged since the 1990s, Ahlenius wrote: "While the initial disclosure of Sweden's institutional but unofficial Cold War connections with Western powers was met with denials and outrage, it was eventually accepted as the new truth. Thus, the revelation of stay-behind networks is often treated more like a romantic spy adventure than a historical fact." She noted that the secret resistance movement established in Sweden, and closely linked with Western powers, was likely initiated by Prime Minister Tage Erlander (Palme's predecessor) along with several ministers.

"[It was] initially led by Alvar Lindencrona, CEO of Thule insurance, three department heads and regional/local 'cells' operated under him," she wrote and added, "meetings occurred in secret rooms in Lindencrona's house or Thule's offices, and funding came from secret sources. Between 1951 and 1953, the CIA under William Colby, stationed in Stockholm and later CIA director, helped establish the network in Sweden, although the Swedes retained top-level control."

Journalist Wall adds some background information: Experience from World War II, he says, showed that countries that were occupied had been unprepared for such an eventuality – there were no resistance movements and they in essence had to be improvised. Thereafter, it was in the interest of those countries and others to prepare properly for the threat of military occupation; in Sweden, various actors dealt with this scenario at an early stage. Immediately after the war, a secret, state-level initiative was launched by the prime minister; the CIA entered the picture in the 1950s. Before that certain extremist elements had worked toward similar aims – among them war veterans who supported the Nazis during the war and volunteered to fight alongside them in the Continuation War in Finland. In the end, these three trajectories evolved into the Sweden's stay-behind network, although it is unclear exactly what remained of them in its final iteration.

"Unlike in other places, despite the cooperation with American and other actors, the Swedish network was established and organized by Swedes," says historian Mats Deland, a senior lecturer at Mid Sweden University (Mittuniversitetet) in Sundsvall. "Sweden did not participate in World War II, but it could learn from the Nazi invasion of Norway in 1940. The Norwegians sank the Blücher, one of the German ships on its way to capture the Norwegian capital in the Oslo fjord, which delayed the Germans and caused them heavy losses, while at the same time giving the Norwegians time to evacuate the royal family and their government northward.

"This experience was important for both the Norwegians and the Swedes who learned from it and came up with the idea to establish an organization that could evacuate the Swedish royal family and the government, but also 'stay behind' and protect the country. This goal of staying behind was the result of another experience from World War II: the NKVD, the Soviet security service under Stalin, who remained behind and became partisans in the German-occupied areas."

So, in the Swedish case, the stay-behind network was not controlled by the Americans or by NATO?

Deland: "Correct, in Sweden this was a local initiative. The Americans arrived a little after the network was established, and even then, they did not take control; they only integrated needs arising from NATO doctrine, which was based on the fact that only the United States had nuclear weapons. In the case of a Soviet invasion and the need for American aircraft to fly over Sweden, the idea was, like the French resistance – and to some extent the Belgian and Dutch resistance – to create escape lines that could smuggle out downed crews. But the United States did not establish the network and did not manage it. This may have changed in 1965, when Swedish security services were reorganized [when the Cold War-era external intelligence agency, T-kontoret, and internal intelligence agency, B-kontoret, merged into a single, secret organization], partly with the involvement of Olof Palme. It is possible that American involvement increased then."

How much was the Swedish stay behind network controlled by the state, and how much of its activity was conducted by civilian or military actors without the knowledge or control of the political leadership?

"Between 1947 and 1951, there were many volunteers in the network, including people who had served alongside the Germans during World War II, some of whom were highly problematic. Because of these types, the secret police discovered the network even though they were not supposed to know about it. Only the people directly involved – Prime Minister Erlander and a small part of the security apparatus – were meant to be 'in the loop.' Following this discovery, which angered Erlander and the security apparatus greatly, the network was reorganized, removing the problematic elements and incorporating trade union members and the business sector."

According to Deland – and in keeping with Ahlenius' observations, as mentioned – the network was indeed led by executives such as Alvar Lindencrona, the head of the Thule company, a businessman with relatively progressive social views for his time, and it recruited forces from the trade unions that had a traditional affinity to the ruling Social Democratic Party. "These were ordinary people," he says, "not former soldiers. Although they needed training, they could be trusted, and the network remained secret until the 1990s." In other words, even though neither the Swedish parliament nor the rest of the government knew about the network, it was indeed an official entity. Indeed Deland notes that a recent book revealed an interesting document: an official government decision from the 1950s forming Sweden's stay-behind network, showing that it was legal and above board. The diaries of Prime Minister Erlander show that he may have given it a green light as early as 1947.

The book Deland refers to is Johan Wennström's "Sweden's Cause Was Our Cause: The Secret Swedish Resistance Movement" (2023). Wennström calls his country's stay-behind underground a "resistance movement," and reveals that the organization's code name, used by its members at the time, was Metro. Wennström says Metro was not established or controlled by NATO and it did not act on the latter's behalf, although he confirms there was cooperation with MI6 in Britain and, to some extent, with the CIA, mainly concerning programs such as evacuating Swedish decision-makers to England if necessary.

Furthermore, Wennström writes, Metro likely included several hundred people, as well as a sort of "invisible combat unit" that could expand to as many as 3,000. The underlying principle was that the network's members would recruit additional people from their immediate circle if necessary. The author also describes the group's structure was fairly cooperative, with representation from various sectors of Swedish society; information about its activities, he says, was distributed on a strict "need-to-know" basis. The organization was formally legalized in 1955, having been mandated by an earlier government decision. Typically, it was involved in organizing potential resistance and civil defense activities, such as mapping escape routes, planning acts of sabotage of critical infrastructure that could fall into Soviet hands, rescuing government officials and storing weapons. Wennström does not know when the organization ceased to exist, or if it exists today.

The phenomenon remains highly controversial and difficult to research, yet there's general agreement that stay-behind networks existed in Europe, operating without parliamentary oversight and known to few decision-makers.

Regarding other countries that had stay-behind networks, it is clear, both from Wennström's book and other sources, that heterogeneity was the keyword. Each country built its organization differently depending on perceived threat and the nature of the country's political, military and industrial power structures. Even in NATO member states, the networks were not necessarily under that organization's control. Parliamentary or public oversight was generally minimal, and there is still controversy over what their involvement was in domestic activity beyond preparing for a possible Soviet invasion during the Cold War era.

One of those who has focused on the phenomenon at the European level is Swiss author and researcher Daniele Ganser, whose controversial 2005 book – "NATO's Secret Armies: Operation Gladio and Terrorism in Western Europe" – is one of the best-known on the subject. It received praise but also criticism by some who claim that it is based on an unsubstantiated conspiracy. In it Ganser claims that Western intelligence networks operated secretly in Allied countries during the postwar era, sometimes beyond the bounds of proper legal and political oversight. He cites Italy, Belgium, France, Germany, Switzerland, the Netherlands, and Turkey, emphasizing that in some of these countries the stay-behind networks were indeed involved in terrorism, false-flag operations and political manipulation.

Mats Deland collaborated with Ganser on the Swedish edition of the book, which includes a chapter on the possible connection to the Palme assassination.

Did Prime Minister Olof Palme know about the network?

Deland: "We know he was aware of it during the tenure of his predecessor, Erlander, because he worked on it as one of Erlander's people in the 1950s. What he knew later, we do not know for certain. But it is reasonable to assume that all prime ministers knew about the network, although there are no official documents on the matter."

What can be said, to the best of your knowledge, about the Swedish stay-behind network in the 1980s, during Palme's second government?

"We don't know. We have some information about the network in the 1950s, but very little about the 1980s."

When did suspicions arise about a connection between the network and Palme's assassination?

"These were suspicions that arose from the very beginning. There was an investigative attempt as part of the official inquiry, and there were also discussions about people from the Stockholm police who could have been involved in the murder, but these are speculations and I do not deal with them."

Sometimes it's difficult to know whether a fact uncovered in an investigation is the key to solving a (murder) mystery or just a coincidence. The last person suspected of killing Prime Minister Palme, Stig Engström, who died 26 years ago, was nicknamed the "Scandia Man" because his workplace was in a building called the Scandia building. The building had previously housed the headquarters of the above-mentioned Thule insurance company Thule merged with Scandia in the 1960s and was run by Alvar Lindercrona who, as said, apparently headed country's the stay-behind network; indeed some of its meetings took place in that same building. In other words, if Engström murdered Palme, he did so while leaving a place where in the past – and possibly as late as the 1980s – meetings of senior members of the country's stay-behind network were held. Is this a coincidence? And even though there is no evidence that Engström was actually connected to the underground organization, is there any logic to the claim that it was involved in Palme's murder?

Wall, the journalist, is not unequivocal on this matter, but he does suggest some key historical points that should be taken into account. "One of the things that happened during Palme's second term as prime minister in the 1980s was a series of alleged Soviet submarine incursions into Swedish territorial waters," he explains. "These incidents caused a severe security crisis, and some argued that they were preparations for an invasion and the establishment of espionage infrastructure. Within the Swedish security establishment, there were claims that Palme did not take the threat seriously and that, because of this, he posed a security risk to Sweden.

"Furthermore, Palme was supposed to travel to Moscow to meet Soviet leader Mikhail Gorbachev in April 1986. Palme, who returned to serve as prime minister in 1982, was active on the international stage on issues of arms reduction and nuclear disarmament. His opponents argued that he had close and controversial ties to the Soviet Union, although a more balanced description would be that he was open to discussions with Soviet leaders about disarmament – something that went against both NATO's view and the opinions of senior Swedish military officials. The assassination on February 28, 1986, meant that it was Palme's successor, Ingvar Carlsson, who met Gorbachev."

As far as is known, the issue of disarmament was not on the agenda at that Swedish-Soviet summit.

Wall adds that there were a number of people who claimed to have received offers to kill Olof Palme; in several cases, it was suggested that Swedish intelligence services were behind those offers. But no one known to have actually belonged to any of these secret services has ever come forward to confirm that they were approached. Wall also provided Haaretz with documents he's collected showing that evidence indicating that people with radio devices were present in the area on the night of the assassination was not taken seriously by the investigators. He does not claim that there is proof that the murder was organized by political actors, but argues that it is certainly a line of inquiry worthy of serious examination.

And he is not alone: Ahead of the 40th anniversary of the assassination, a public appeal was launched to encourage the Swedish government and parliament to establish a "truth commission" to finally resolve any outstanding questions.

"On February 28, 1986, Olof Palme fell victim to a brutal attack on an open street in central Stockholm," the appeal begins. "The assassination of the prime minister of Sweden was a unique attack on our democracy. In a country governed by the rule of law like Sweden, everything possible should have been done to solve this murder. The fact that it remains unsolved 40 years later is unacceptable, especially when not all possibilities for an indisputable and absolute solution have been investigated."

The text cites problems that may have prevented discovery of the truth – still-classified archives, false answers given to the investigators by secret service personnel and investigative files that have disappeared. Possible involvement of the Swedish stay-behind network is also mentioned, and the conclusion is: "This is the only assassination of a political leader in modern Europe that may remain unsolved. Clarifying all the circumstances surrounding Olof Palme's murder will strengthen Sweden."

Still, at this rate, it is doubtful whether the mystery will ever be solved. Even if it is, the relatively recent revelations regarding stay-behind networks in Europe are just another example of how, even if and when the public discovers the truth, it sometimes comes decades too late, in the form of very old news.