We study two different varieties of uncertainty that countries can face in international crises and establish general results about the relationship between these sources of uncertainty and the possibility of peaceful resolution of conflict. Among our results, we show that under some weak conditions, there is no equilibrium of any crisis bargaining game that has voluntary agreements and zero probability of costly war. We also show that while uncertainty about the other side's cost of war may be relatively benign in peace negotiations, uncertainty about the other side's strength in war makes it much more difficult to guarantee peaceful outcomes. Along the way, we are able to assess the degree to which particular modeling assumptions found in the existing literature drive the well-known relationship between uncertainty, the incentive to misrepresent, and costly war. We find that while the theoretical connection between war and uncertainty is quite robust to relaxing many modeling assumptions, whether uncertainty is about costs or the probability of victory remains important.