For four decades, a network of secret soldiers operated across Western Europe, hidden from elected governments and accountable to no parliament. These NATO stay-behind armies were armed with machine guns, explosives, and high-tech communications equipment, all buried in underground bunkers and forest caches. Their official purpose was to resist a Soviet invasion that never came. Their unofficial legacy is far darker.
On 24 October 1990, Italian Prime Minister Giulio Andreotti stood before his country’s parliament and confirmed what investigators had suspected for years: a clandestine paramilitary organization called Gladio had been operating inside Italy since the early 1950s.[s] Andreotti described a “structure of information, response and safeguard,” listing 622 civilian operatives and 127 weapons caches that had since been dismantled. The revelation sent shockwaves across the continent, because Italy was not alone.
NATO Stay-Behind Armies: Built for War, Active in Peace
The origins of NATO stay-behind armies trace to the early Cold War, when Western leaders feared Soviet tanks rolling across the plains of Western Europe. Drawing on Britain’s wartime experience with the Special Operations Executive, which had organized resistance networks in Nazi-occupied territory, the CIA and British MI6 began building clandestine cells in country after country.[s]
These networks operated under different code names in each country: Gladio in Italy, SDRA8 in Belgium, P26 in Switzerland, Absalon in Denmark, ROC in Norway. By the late 1950s, coordination ran through two NATO committees at Supreme Headquarters Allied Powers Europe (SHAPE): the Clandestine Planning Committee, established around 1951, and the Allied Clandestine Committee, created in 1957.[s]
The operatives were trained in sabotage, guerrilla warfare, escape routes, and clandestine communications. Arms caches contained C4 plastic explosives, submachine guns, and radio equipment. In Belgium alone, a 1991 inventory listed around 300 weapons, including M1 carbines and MP40 submachine guns, plus “armes en cocon,” weapons packaged for long-term underground storage.[s]
Italy’s Years of Lead and the Strategy of Tension
Italy endured a period of extraordinary political violence from 1968 to the mid-1980s known as the Years of Lead (Anni di piombo), which left 428 people dead and approximately 2,000 injured.[s] Bombings, assassinations, and kidnappings came from both far-left and far-right groups. But a pattern emerged in the deadliest attacks: bombs placed in public spaces, initially blamed on left-wing groups, later traced to neo-fascist organizations with apparent links to Italian intelligence services.
The Piazza Fontana bombing on 12 December 1969 killed 17 people and wounded 88 at a Milan bank.[s] Police initially arrested anarchists. One suspect, Giuseppe Pinelli, died after falling from a fourth-floor police station window during interrogation. Decades of trials eventually attributed the attack to the neo-fascist group Ordine Nuovo.[s]
The Bologna railway station bombing on 2 August 1980 was even deadlier: 85 people killed, over 200 wounded, making it Italy’s deadliest postwar terrorist attack and one of Europe’s deadliest postwar attacks, though not Europe’s overall deadliest—the 1988 Lockerbie bombing killed 270 people, far more than Bologna’s 85.[s] Members of the neo-fascist Nuclei Armati Rivoluzionari were eventually convicted, and later investigations identified Licio Gelli, head of the secretive Propaganda Due (P2) Masonic lodge, as the mastermind.[s]
This pattern of violence carried a name: the strategy of tension, a political tactic in which terrorist attacks create widespread fear, pushing the public to demand stronger, more authoritarian government.[s]
The Vinciguerra Testimony
The clearest connection between these NATO stay-behind armies and political violence came from an unlikely source: a convicted terrorist who decided to talk. Vincenzo Vinciguerra, a neo-fascist serving a life sentence for the 1972 Peteano car bombing that killed three Carabinieri, testified in 1984 about a “super-organisation” operating within the Italian state.[s]
Vinciguerra described “a secret force parallel to the armed forces, composed of civilians and military men, in an anti-Soviet capacity.” When the Soviet invasion failed to materialize, he said, this force “took up the task, on NATO’s behalf, of preventing a slip to the left in the political balance of the country.”[s]
Prosecutor Felice Casson investigated whether explosives used in the Peteano bombing could be traced to a NASCO stay-behind cache at Aurisina, near Trieste and only a few kilometres from the attack site—not to a dump beneath a cemetery near Verona. Later judicial analysis did not conclusively establish that provenance, and some accounts describe ordinary construction explosive rather than military C4.[s] The investigation also revealed that an explosives expert working for the Italian police, a member of Ordine Nuovo, had deliberately falsified his analysis to blame the Red Brigades. It was Casson’s dogged investigation that ultimately forced Andreotti to admit Gladio’s existence to parliament.
Belgium: The Brabant Killings
Italy was not the only country where NATO stay-behind armies intersected with unexplained violence. In Belgium, a group known as the Brabant killers carried out a series of attacks between 1982 and 1985, killing 28 people and injuring 22 in raids on supermarkets, restaurants, and arms dealers.[s]
The killings were bizarre. The attackers used military-grade weapons, including rare buckshot similar to that used by a former Belgian Gendarmerie special forces unit. Their robbery proceeds were modest relative to the extreme violence. Several authors and a BBC documentary linked the attacks to NATO’s stay-behind network and the far-right group Westland New Post.[s]
A Belgian parliamentary inquiry investigated these connections but found no conclusive proof of Gladio involvement in the attacks. The Brabant killers were never identified. Belgian authorities closed the principal investigation in June 2024 without convictions, though additional investigative measures were authorized in January 2025 after an appeal and a new lead; the case remains among Belgium’s most notorious unsolved crime sprees.
The 1990 Reckoning
After Andreotti’s October 1990 revelation, the dominoes fell quickly. Belgian Defense Minister Guy Coëme and Prime Minister Wilfried Martens confirmed their country’s stay-behind network on 7 November 1990.[s] In Switzerland, the exposure of the P26 secret army, found to harbor “an extremist ideology far removed from mainstream political thought,” triggered a political crisis that led to a full parliamentary investigation.[s]
On 22 November 1990, the European Parliament passed a resolution condemning “the clandestine creation of manipulative and operational networks.” The resolution noted that “in certain Member States military secret services (or uncontrolled branches thereof) were involved in serious cases of terrorism and crime.”[s] It called on all member states to dismantle clandestine military networks and establish parliamentary committees of inquiry.
The resolution also protested “vigorously at the assumption by certain US military personnel at SHAPE and in NATO of the right to encourage the establishment in Europe of a clandestine intelligence and operation network.”[s] The Bush administration refused to comment. Only Italy, Belgium, and Switzerland carried out full parliamentary investigations.
What the Parliamentary Investigations Revealed
In 2000, a proposed report by center-left members of the Italian parliamentary commission asserted that a strategy of tension had been “supported by the United States to stop the PCI, and to a certain degree also the PSI, from reaching executive power in the country.”[s] PCI was the Italian Communist Party; PSI, the Italian Socialist Party.
The commission stated that “US intelligence agents were informed in advance about several terrorist bombings, including the December 1969 Piazza Fontana bombing in Milan and the Piazza della Loggia bombing in Brescia five years later, but did nothing to alert the Italian authorities or to prevent the attacks from taking place.”[s]
The US State Department rejected these allegations, maintaining that the NATO stay-behind armies served only to resist a potential Soviet invasion and had no role in domestic terrorism. Historian Peer Henrik Hansen and other scholars have also questioned some of the more sweeping claims about direct NATO control of terrorist operations, noting that the evidence for a centrally directed “strategy of tension” remains contested.
Legacy
Operation Gladio remains one of the Cold War’s most disturbing episodes. What is established beyond reasonable doubt: NATO and the CIA created secret paramilitary networks across Western Europe that operated for roughly 40 years outside any democratic oversight. These networks maintained hidden arsenals and trained operatives in unconventional warfare.
What remains contested: the degree to which these networks, or rogue elements within them, actively participated in or enabled the political violence that scarred Italy, Belgium, and other countries during the Cold War decades. The European Parliament concluded that military secret services were “involved in serious cases of terrorism and crime.” Italian courts convicted neo-fascists with documented ties to intelligence services. Casson investigated a possible link between Peteano and a stay-behind arms cache at Aurisina, but courts did not conclusively establish that explosives from Gladio caches were used in a terrorist attack.
But a direct chain of command from NATO headquarters to specific terrorist bombings has never been proven. The full truth may remain buried, like the weapons caches beneath Italian cemeteries, because many of the participants are dead, the documents remain classified, and the institutions involved have shown little appetite for transparency.
What Gladio demonstrates without ambiguity is the danger of unaccountable military structures operating within democratic states. The European Parliament’s 1990 resolution remains a warning: when secret armies escape all democratic controls, the line between defending a society and undermining it can vanish entirely.
For four decades, a clandestine network of paramilitary operatives operated across Western Europe, financed by the CIA, coordinated through NATO’s command structures, and hidden from parliaments, courts, and the public. These NATO stay-behind armies were armed with machine guns, C4 plastic explosives, and encrypted communications equipment stored in underground bunkers. Their stated purpose was to organize guerrilla resistance in the event of a Warsaw Pact invasion. The invasion never came. What came instead was a decades-long pattern of political violence whose connections to these secret networks remain among the most contested questions in Cold War historiography.
On 24 October 1990, Italian Prime Minister Giulio Andreotti confirmed before the Chamber of Deputies the existence of Gladio, a clandestine stay-behind organization embedded within Italy’s military intelligence apparatus since the early 1950s.[s] Andreotti described a “structure of information, response and safeguard,” identifying 622 civilian operatives and reporting that 127 weapons caches had been dismantled. His disclosure was not voluntary: it was forced by the persistent investigations of Venetian magistrate Felice Casson, whose prosecution of the 1972 Peteano bombing had uncovered an arms trail leading directly to NATO-linked depots.
Origins of NATO Stay-Behind Armies
The institutional architecture of the NATO stay-behind armies grew from Britain’s wartime Special Operations Executive (SOE), which had coordinated resistance networks across Nazi-occupied Europe. After 1945, British and American intelligence services began constructing analogous networks to prepare for a potential Soviet occupation of Western Europe.[s]
In 1948, Belgian Prime Minister Paul-Henri Spaak authorized the Staatsveiligheid to negotiate a clandestine stay-behind structure with British SIS chief Sir Stewart Menzies and the CIA.[s] By 1949, the Western Union Clandestine Committee (WUCC) was coordinating stay-behind operations among Belgium, the Netherlands, Luxembourg, France, and Great Britain. This framework transferred to NATO structures around 1951 when the Supreme Allied Commander Europe (SACEUR) established the Clandestine Planning Committee (CPC) at SHAPE.
In 1957, the United States, United Kingdom, France, and Benelux countries established the Allied Clandestine Committee (ACC), later renamed the Allied Coordination Committee. This body coordinated multinational exercises and provided policy guidance on stay-behind matters. CIA representatives attended every meeting, though officially without voting rights.[s] General Gerardo Serravalle, who commanded Italian Gladio from 1971 to 1974, confirmed that “at the stay-behind meetings representatives of the CIA were always present.”
These networks operated under distinct code names across the continent: Gladio in Italy, SDRA8 in Belgium, P26 in Switzerland, Absalon in Denmark, ROC in Norway, I&O in the Netherlands. Each country maintained its own arsenal. A 1991 Belgian inventory documented approximately 300 weapons, including M1 carbines and World War II-era MP40 submachine guns, alongside inflatable boats and video surveillance equipment.[s]
Italy: The Strategy of Tension and NATO Stay-Behind Armies
Italy’s experience with its stay-behind network is the most extensively documented and the most troubling. The country’s Years of Lead (Anni di piombo), stretching from 1968 to the mid-1980s, produced 428 deaths and roughly 2,000 injuries from thousands of terrorist attacks by groups on both the far left and far right.[s]
The term “strategy of tension” (strategia della tensione) first appeared in The Observer on 14 December 1969, two days after the Piazza Fontana bombing, describing a political tactic whereby violent attacks create widespread fear, pushing the populace toward authoritarian governance.[s] The pattern was consistent: indiscriminate bombings in public spaces, initially attributed to left-wing groups, later traced through decades of trials to neo-fascist organizations with documented connections to Italian military intelligence.
Piazza Fontana, 1969
On 12 December 1969, a bomb exploded at the Banca Nazionale dell’Agricoltura in Milan’s Piazza Fontana, killing 17 and wounding 88.[s] The same afternoon, another bomb detonated in a Roman bank, and a third was found unexploded at the Tomb of the Unknown Soldier. Police arrested anarchists, including Pietro Valpreda, who spent three years in preventive detention before eventual acquittal. Anarchist railway worker Giuseppe Pinelli died during interrogation after falling from a fourth-floor window at Milan’s police headquarters.
After a tortuous sequence of trials spanning decades, Italian courts attributed the bombing to the neo-fascist organization Ordine Nuovo, founded by Pino Rauti.[s] Judge Guido Salvini’s investigations revealed that Ordine Nuovo had “collaborated very closely” with the Italian Military Secret Service (SID). General Gianadelio Maletti, head of SID’s counterintelligence section and a member of the P2 lodge, was convicted of obstructing the investigation and destroying evidence to protect right-wing groups.
Bologna, 1980
The deadliest single attack came on 2 August 1980, when a time bomb hidden in a suitcase detonated in the air-conditioned waiting room of Bologna Centrale railway station, killing 85 people and wounding over 200.[s] It was Italy’s deadliest postwar terrorist attack and one of Europe’s deadliest postwar attacks, though not Europe’s overall deadliest—the 1988 Lockerbie bombing killed 270 people, far more than Bologna’s 85.[s]
The investigation was sabotaged from within. SISMI Generals Pietro Musumeci and Belmonte, both P2 members, planted false evidence to divert investigators toward other suspects. Members of the neo-fascist Nuclei Armati Rivoluzionari were eventually convicted, and in 2022, Paolo Bellini was convicted of direct involvement in the massacre and sentenced to life imprisonment. Later court proceedings identified Licio Gelli, grand master of the P2 Masonic lodge, as the mastermind.[s]
Historian Tobias Hof has argued that the 1980 bombing should be understood in the context of renewed Cold War tensions following the Soviet invasion of Afghanistan in 1979, which reinvigorated anti-communist networks across Europe and “again offered an opportunity to form alliances with the conservative milieu, including elements of the state secret services.”[s]
The Vinciguerra Testimony
The most direct testimony connecting NATO stay-behind armies to political violence came from convicted neo-fascist Vincenzo Vinciguerra, who was serving a life sentence for the 1972 Peteano car bombing that killed three Carabinieri.[s] Prosecutor Casson pursued a disputed theory that explosives used in the attack might be traced to a NASCO stay-behind cache at Aurisina, near Trieste, rather than a Gladio dump beneath a cemetery near Verona; later judicial analysis did not conclusively establish that link, and some accounts describe ordinary construction explosive rather than C4. Casson’s investigation also showed that a police explosives expert who was an Ordine Nuovo member had deliberately falsified his analysis to blame the Red Brigades.[s]
In 1984, Vinciguerra testified about “a secret force parallel to the armed forces, composed of civilians and military men, in an anti-Soviet capacity.” He stated that this force, “lacking a Soviet military invasion which might not happen, took up the task, on NATO’s behalf, of preventing a slip to the left in the political balance of the country. This they did, with the assistance of the official secret services and the political and military forces.”[s]
The 2000 Parliamentary Commission
A proposed 2000 report by center-left and Left Democrat members of the Italian parliamentary commission—not adopted as the commission’s collective finding—argued that “a strategy of tension had been supported by the United States to stop the PCI, and to a certain degree also the PSI, from reaching executive power in the country.” The commission further asserted that “US intelligence agents were informed in advance about several terrorist bombings, including the December 1969 Piazza Fontana bombing in Milan and the Piazza della Loggia bombing in Brescia five years later, but did nothing to alert the Italian authorities.”[s]
The report’s conclusions were politically contested. Historian Aldo Giannuli, who served as a consultant to the parliamentary terrorism commission, characterized the left-wing coalition’s report as “dictated primarily by domestic political considerations rather than historical ones.” The US State Department rejected the allegations entirely, maintaining that the stay-behind program served only defensive purposes.
Belgium and the Brabant Killings
Belgium’s stay-behind network, operational from 1951 to its dissolution in November 1990, consisted of two branches: SDRA8 under military intelligence, and STC/Mob under the civilian Staatsveiligheid.[s] The military branch trained operatives in “unorthodox warfare, combat and sabotage, parachute jumping and maritime operations.”
Between 1982 and 1985, the Brabant killers carried out a series of exceptionally violent raids on supermarkets, restaurants, and arms dealers, leaving 28 dead and 22 injured.[s] The attackers used military-grade weapons, including rare buckshot similar to that issued to the Belgian Gendarmerie’s Group Diane special forces unit. Their robbery proceeds were disproportionately small given the extreme violence employed.
Several researchers and a BBC documentary linked the Brabant killings to NATO’s stay-behind network and the far-right Westland New Post organization.[s] Journalist René Haquin alleged that the United States had attempted to “toughen up” Belgian policing in the 1970s, and when those methods were rolled back, sought to force the government’s hand through destabilization. However, the Belgian parliamentary inquiry found no substantive evidence that the stay-behind network was directly involved in the attacks. Belgian authorities closed the principal investigation in June 2024 without identifying the perpetrators, though additional investigative measures were authorized in January 2025 following an appeal and a new lead.
The 1990 Revelations and European Parliament Response
Andreotti’s disclosure triggered a cascade of admissions. Belgian leaders confirmed their network on 7 November 1990. In Switzerland, exposure of the P26 secret army, found to harbor “an extremist ideology far removed from mainstream political thought,” triggered a political crisis and a full parliamentary investigation into its activities.[s]
On 22 November 1990, the European Parliament passed a formal resolution condemning the NATO stay-behind armies. The resolution stated that “for over 40 years this organization has escaped all democratic controls and has been run by the secret services of the states concerned in collaboration with NATO.” It noted that “in certain Member States military secret services (or uncontrolled branches thereof) were involved in serious cases of terrorism and crime as evidenced by various judicial inquiries.”[s]
The resolution called on all member states to dismantle clandestine military networks, establish parliamentary committees of inquiry, and clarify any links between these organizations and terrorist groups. It protested “vigorously at the assumption by certain US military personnel at SHAPE and in NATO of the right to encourage the establishment in Europe of a clandestine intelligence and operation network.”[s]
Despite this resolution, only Italy, Belgium, and Switzerland conducted full parliamentary investigations. The Bush administration declined to comment. NATO itself has never issued a comprehensive accounting of the stay-behind program.
Historiographic Debate
The scholarly literature on Operation Gladio divides into two broad camps. Swiss historian Daniele Ganser’s NATO’s Secret Armies (2005) argues for direct NATO involvement in right-wing terrorism as part of a coordinated strategy of tension. Ganser’s work has been criticized by reviewers including Peer Henrik Hansen and Philip H.J. Davies, who question his reliance on contested documents, particularly US Army Field Manual 30-31B, which the US State Department claims is a 1976 Soviet forgery while others, including former CIA Deputy Director Ray S. Cline, have suggested it may be authentic.
Italian historian Anna Cento Bull’s Italian Neofascism: The Strategy of Tension and the Politics of Nonreconciliation (2012) provides a more nuanced account, examining how far-right groups exploited Cold War structures while maintaining their own autonomous agendas. Tobias Hof’s analysis emphasizes the transnational dimension of right-wing terrorism in 1980, connecting the Bologna bombing to similar attacks in France, Spain, and Germany during the same period.[s]
What is not in dispute: NATO and the CIA built secret paramilitary networks across Western Europe that operated for roughly 40 years without democratic oversight. These networks maintained hidden arsenals. Prosecutorial work raised disputed claims about Peteano and a stay-behind cache at Aurisina, but judicial findings did not conclusively establish that Gladio cache explosives were used in a terrorist attack. Italian military intelligence officials were convicted of obstructing investigations into right-wing bombings. And the European Parliament formally found that military secret services were involved in “serious cases of terrorism and crime.”
What remains contested is whether these facts point to a centrally directed campaign of state terrorism, to rogue elements exploiting existing structures, or to opportunistic alliances between neo-fascist terrorists and sympathetic intelligence officers acting without institutional authorization. The full truth may be irrecoverable. Many participants are dead, critical documents remain classified, and the institutions involved have demonstrated minimal interest in self-examination.
Gladio’s enduring significance lies less in resolving these debates than in the principle the European Parliament articulated in 1990: secret armies that “escape all democratic controls” represent an inherent threat to the societies they claim to protect, regardless of their original justification.
