I've always heard that Gladio was NATO mission that was involved in multiple terror attacks by neo-fascist groups. There seem to be plenty of articles pushing said narrative and it even seems to come up in pop culture fairly frequently.
Yet while researching it I found that a lot of historians claim there isn't enough evidence to conclusively tie Gladio to fascist groups or the terror attacks themselves, or claiming stay behind missions were just something a lot NATO countries were doing without the NATO actually having any control over Gladio.
Is there any hard evidence for it Gladio being organized by the NATO? Is there any for Gladio troops being involved in right wing terrorism?
If not, how come this narrative is something that is so wide spread and commonly accepted?
Hi! Historian of nationalism and political culture here! I think I can provide you with a reasonably in-depth answer based off of some of the literature and recent discoveries on Gladio in The Netherlands. Disclaimer: towards the end of the answer I will include a small encore of personal anecdote (please based mods do not ban me, I beseech you).
So the first thing we have to tackle is the mistaken notion that Operation Gladio was an exclusive NATO-related organisation, because it was not. It did operate in NATO member states, but was existed also in parallel security structures in states outside of NATO and/or unaligned to NATO. More on its precise organisational status later on.
Following this prelude we can delve deeper into the actual and exact nature of what brought about Operation Gladio and what it actually constituted. The earliest origins of Gladio can be traced back to the activities of the Special Operations Executive (SOE) - a military arm of the British Ministry of Economic Warfare that was sustained throughout the Second World War. The SOE was tasked with the organisation and execution of resistance and sabotage activities in occupied continental Europe, as well as informal intelligence gathering on (armed) political organisations. Much of the resistance movements in France and the Benelux were assisted in organisation, compartmentalisation, and training by the SOE during the war years. Though the SOE covertly represented British political and military interests on the continent, it did also assist resistance organisations that on the long term could prove threatening to these interests. Examples of this include the communist resistance in France and more famously also the partisan movement led by Tito in Yugoslavia. On the short term the SOE was thus there to fight the Nazi through sabotage and disruption.
A more long-term view emerged towards the end of the Second World War, as competition between the USSR, US, and UK over spheres of influence started mounting. US and UK adversity towards Stalin's agenda had been evident even before the Second World War, and tensions over occupation zones, post-war democratization, and denazification did little to lower tensions. By 1948, Stalin had succeeded in securing a communist victory in elections in Czechoslovakia, had been supporting communist insurgents in Greece, and had very effectively managed to support communist parties in France, Italy, and Germany. Fears of imminent communist takeovers on the western edge of the continent became all too realistic, and diplomatic and military means were invested to keep 'the reds' at bay in Western Europe.
Before the founding of NATO in 1949, the Franco-British Alliance was expanded into the Brussels Treaty Organisation that came to include the Benelux, which later on morphed into the Western European Union. The alliance was exclusively military, and heavily geared towards a common effort against a potential communist invasion. It was also in a more practical sense, a giant knowledge-sharing platform for the militaries of the involved countries. Given the extensive contacts between the Benelux and Britain during the Second World War, and the overall leadership of the war effort in the given region by the British, it isn't hard to see how there was a distinctly British flavour to the alliance. The WEU existed in parallel to NATO until 2011.
During the 1946-51 period veterans of the SOE from the Benelux, France, and Italy together with US and British intelligence specialists wasted no time in conceiving a stay-behind organisation, as a sort of future insurance against a communist invasion. The multinational experience of the SOE (wartime) and teh CIA (post-war/counterinsurgency) laid the groundwork for binary covert organisation, that would not really meet the public eye until the early 1990s, and became known as 'Operation Gladio' (which was the name of its Italian compartment).
The binary elements in the broadest sense constituted a series of operations' cells, and a series of intelligence cells. The intelligence cells would be continually active, whereas the operations cells would only be activated in case of an emergency arising. The overarching command lay with the WEU, which would also be responsible for the coordinated hiding of weapons' caches throughout the predicted theater of war, and the connection of both the intelligence and operations elements to these caches. The Ministries of Defence of each WEU member would be responsible - together with their domestic security apparatusses - for the functioning of the stay-behind organisation and its equipment.
At this point I'm hitting the ceiling on my knowledge of the shape of the organisation as-is. To come to a better understanding of how the narrative emerged surrounding it, and what events led to its exposure the case of 'Gladio' in The Netherlands is probably one of the most accessible ones.
The first generation of ex-SOE men remained in active military service during the '50s and early '60s, but a second generation started being recruited as early as 1954 according to sources at the National Archives, and corroborating Archives of the Ministry of Defence. Throughout the Cold War, the organisation remained active, and recruited new operators and intelligence gatherers in strict secrecy to maintain its coherence. The Dutch intelligence service (AIVD) has provided evidence of some of the payment accounts and 'common' real estate held by the Ministry of Defence (think safehouses etc.) that were in use by the organisation.
The new generations of employees of the organisation experienced the Second World War differently, or not at all, and hence grew up to hold different understandings of political relations and interests. In the Dutch case there is a marked difference in how the pre- and post-war generations view Britain and its continental interests, which was undoubtedly reflected in the membership of 'Gladio'. A further changed factor was the difference in disposition of the pre- and post-war generations towards the use of (political) violence in the given timeframe. The '60s and '70s saw new uses of violence to political ends, and 'Gladio' did not remain untouched by these in the dialectical sense. Where anti-communism in the '50s might've meant defending ones' homeland against an expected invasion, in the '70s it increasingly meant taking direct action to sustain clandestine activity aimed at overthrowing public order or a regime.
The clandestine nature of Gladio meant that complex bureaucratic actions like vetting ones' employee were largely impracticable, which combined with the political volatility meant that 'undesirables' in the form of terrorist adventurers, common criminals, and otherwise violent groups were hypothetically able to gain access directly or indirectly to equipment or intelligence of the organisation, and use it for their own ends. In Belgium and Switzerland government probes of the early 2000s revealed that no such cases had been documented, but that it remained plausible. It is similarly hypothesised that far-right groups in Italy forced their way into multiple weapons' caches, for actions that include the infamous bombing of the Bologna train station. In the Netherlands there is some circumstantial (but initially quite stark) evidence that our currently rather famous crime boss Willem Holleeder and his co-criminal John Mieremet acquired weapons from a Gladio cache to commit the abduction of the heir to the Heineken imperium in the '90s.
The overall lack of a central infrastructure, the continual lack of official statements regarding its status, and sensationalised press of the early 1990s are thus the main contributors to the notion that Operation Gladio is directly associated with terrorist violence. The fact that intelligence services such as the CIA were involved added to the mystic of 'fascist insurgency', though in the cases of Greece, Spain, Italy, Portugal, and Turkey were actually evidenced by clandestine brutalities meted out on a wide range of both communist and civic organisations.
So, before I get to the encore, my sources on this are the following:
Which brings us to the encore: a lot of the gaps between the literature I was suprisingly enough able to fill out by way of my late grandfather's personal archive and effects. During the Second World War he was agent for the SOE in The Netherlands in a SIGINT capacity, and until at least 1952 remained attached to it formally. Later on it seems that he was closely connected to the Dutch arm of a stay-behind, and potentially assisted other such organisations across Europe since he travelled extremely frequently. Several speeches diary entries and speeches he held for the rotary in 1990-91 mention Gladio, and explain among other things the functioning of the payment systems, the recruiting of 'third parties', and digging up of caches by the Ministry of Defence for mothballing, deactivation or destruction.