In December 2015, the African Union (AU) took the unprecedented step of threatening to use military force against the government of Burundi's wishes in order to protect civilians caught up in the country's intensifying domestic crisis. This article traces the background to this decision and analyses the effectiveness and credibility of the AU's use of coercive diplomacy as a tool of conflict management. After its usual range of conflict management tools failed to stem the Burundian crisis, the AU Commission and Peace and Security Council tried a new type of military compellence by invoking Article 4(h) of the Union's Constitutive Act. We argue that the threatened intervention never materialised because of (1) the Burundian government's astute diplomacy and (2) several African autocrats’ resistance to setting a precedent for future interventions where concerns about civilian protection might override state sovereignty.