This thesis examines whether NATO’s air operation Allied Force was appropriate to expect concession when compelling the Serbian leader Slobodan Milosevic, or if there were other circumstances to explain the NATO failure of success. I analyse the conditions in accordance with previous research and theories of compellent threats. I find that NATO’s efforts meet the expectations for successive coercion and therefore it has to be other explanations why they failed. I argue that NATO misjudged Milosevic when he did not follow the tacit and expected rules of reaction and behaviour, which explains why the outcome became unpredictable and resulted in failure. To complete the theories of successful compellent threats, I suggest that future research should consider the target states strategic culture and ethnic, cultural and historical heritage as well as the state’s public defense will and leadership.