A century of coalitions in battle: Incidence, composition, and performance, 1900-2003

Under what conditions do battlefield coalitions fight as greater or less than the sum of their parts? Introducing Belligerents in Battle dataset, which contains information on actors fighting 492 battles during interstate wars waged between 1900 and 2003, we present, for first time, a portrait universe coalitions. Battlefield win more often suffer fewer casualties belligerents alone. including forces fielded by United States, states with pre-existing treaty agreements, democracies are particularly powerful. By contrast, that include non-state lose majority fights.