This paper provides new insights into the link between the experience of vio- lent conflict and local collective action. I use the temporal and geographical information from four rounds of survey data from Nigeria to relate measures of cooperation to past and future incidences of communal conflict. I show that local collective action, measured in terms of community meeting attendance and volunteering, is highest before the out- break of violence – higher than both post-conflict levels and the generally lower levels ofcooperation in regions not affected by violence. I develop a ‘mobilisation mechanism’ toexplain these findings, arguing that, rather than being an indicator of ‘social capital’, col- lective action ahead of communal violence is inherently ambiguous, and driven by a form of situationally adaptive (and potentially aggressive) ‘solidarity with an edge’. I furthershow that the positive link between previous exposure to civil war-type violence and co- operation holds for Nigeria, too, but that it holds for rural areas only.