In this article, we introduce and utilize a new dataset that provides battle- and war- level Loss Exchange Ratios (LERs) for combatant states involved in multilateral wars between 1816 and 1990.The battle-level data provide an alternative to the widely used, but problematic, HERO/CDB-90 data set on battle outcomes. To demonstrate the utility of the new data, we weigh in on the debate over democratic military effectiveness arguments by replicating models by Reiter and Stam (2002, 2009) and Downes (2009), finding that, when effectiveness is measured using LERs, democracies do not have an edge over their non-democratic counterparts.