ABSTRACT This paper examines the effectiveness of bluffing about external intervention in shaping civil war dynamics using an agent-based model. It argues that warring parties’ initial information levels about interveners and their learning processes determine the success of bluffing. The model explores three scenarios: 1) accurate initial expectations and informative signals 2) inaccurate initial information and uninformative signals and 3) heterogeneous information sets and varied signal updates. Findings suggest bluffing is most effective when both sides start with inaccurate expectations and update slowly. The model’s implications are analyzed through cases in El Salvador, the Warsaw Uprising and South Vietnam negotiations.