The years 1980-1981 witnessed youth revolts all over Western Europe. Influenced by radical politics and punk subculture, youths squatted houses and demanded autonomous, self-managed youth centres and clashed with the police. Out of these revolts grew a radical urban youth movement in which radical politics and youth cultures merged: the squatter or autonomous movement. It was a libertarian movement committed to direct actions against urban renewal projects, militarism, sexism and racism. This movement played an important role in major political controversies such as the placement of midrange nuclear missiles, nuclear energy, the draft and urban development. It posed the militant wing of these broad protests and was a central social movement actor. This research reconstructs, analyses and compares the history of autonomous movements in Amsterdam and Hamburg during the 1980s, especially with regards to (the debates on) militant action. The militant stance and civil disobedience that was central in the movement’s tactics often led to accusations of the movement being inherently violent. Both the media and authorities often claimed that the autonomous movement used indiscriminate and boundless violence. Within the movement too, the limits of militant action often led to heated debates. Debates not only revolved around the actions of activists during clashes with the police, for example during evictions or demonstrations, but also around the movement’s clandestine actions and its attitudes towards armed underground cells such as the Rote Armee Fraktion (RAF), an ultra left organisation which in the 1980s executed campaigns of targeted killings of company directors and high political functionaries. Especially in Germany, authorities and conservative media expressed concerns that the autonomous movement would spawn armed struggle groups or support groups such as the RAF. This research however shows that – although militancy played a central role in the movement’s self-perception – in practice it adhered to specific rules and codes of conduct, which set clear limits to what actions were acceptable and which ones were not. These rules applied to the whole of the movement’s protest repertoire, which consisted of squatting actions and the defence of occupied spaces, militant demonstrations and street fights and, finally, (illegal) sabotage actions. Sabotage actions consisted of an array of practices, from spray painting and petty vandalism to fire bombings. Through thick descriptions and close analysis of specific cases studies and debates, these codes are 8 unravelled. The international scope of the research successively shows that these codes remained largely the same in different political contexts. With regards to militant action in defence of squatted houses, the Grote Keyser in Amsterdam and the Hafenstrasse in Hamburg play a central role in the research. Both were barricaded and the autonomous activists expressed their willingness to defend the building against eviction. However, in the Grote Keyser, long drawn debates unfolded over the use of Molotov-cocktails, which a majority found too dangerous to use. In the Hafenstrasse, the squatters decided against the use of all too large or dangerous projectiles which – if used – could endanger the lives of police officers, such as refrigerators. Self-defence was deemed legitimate, but this was not the case for potentially lethal violence against opponents. Not only with relation to squatting actions, there were codes of conduct. Also during militant demonstrations and street fights, the movement expressed a reluctance to use - potentially lethal - violence against persons, if they were not in danger themselves. When in Amsterdam, a police officer fell off his horse during a riot, autonomous activists stopped throwing stones, discussed the situation and decided to help the man back on his horse. Only after he had returned to his colleagues, the confrontation continued again. An activist later remembered: ‘you’d think “this is the end for this poor man”. But the squatters simply got him back in his saddle.’ With sabotage actions, the codes were more or less the same. Fire bombings were the most extreme form of action the movement used. However, again violence against persons was considered off limits. Instead, the fire attacks aimed at causing material damage exclusively. Autonomous groups made this explicit in their communiqués, and support of these actions by the movement was directly linked to this. Because the autonomous movement adhered strictly to the above mentioned codes of conduct, its relationship to the RAF was strained. Although many autonomous activists were highly critical of the prison conditions of arrested RAF members, they generally refrained from supporting the cell’s offensive actions. Attempts by RAF supporters to ally with autonomous activists, such as during the 1986 anti-imperialist conference, failed. The action ethics of the movement thus revolved around the belief that militancy was legitimate, but unprovoked or lethal violence was not. Militancy was defined as defensive actions such as during squatter actions or demonstrations or inflicting damage upon material goods. Violence on the other hand was seen as consciously causing serious physical harm to opponents or killing them. These 9 findings are essential for a good understanding of the history of squatter movements in Europe.