Our understanding of history shapes our planning for the future. Assessment of what could have been done in past crises is important to judge fairly the responsibility of individual agents, but is also often used to formulate new rules, regimes and policies. Analyses of past options are counterfactual thought-experiments: Could those responsible have made different decisions, and what would the consequences have been? Despite the centrality of such analyses, there is only a limited literature on their scientific foundation. This book proposes criteria for validity and plausibility of counterfactual analyses of historical cases. The armed conflicts in Bosnia and Herzegovina in the 1990s were critical for the formation of key international legal rules and regimes, as well as for our thinking on possible diplomatic and military responses to subsequent armed conflicts. The second part of the book discusses three counterfactual hypotheses about how the conflicts could have been stopped, by a) increased diplomatic pressure, b) use of ground troops to implement a peace agreement in 1993, and c) use of early air strikes to enforce peace. In assessing these hypotheses, the book attempts to shed light both on the course of the conflicts, and on the general possibilities and limitations of using historical experience to draw lessons for the present or future.