Warfare has been found to have detrimental impacts on biodiversity due to its long-lasting economic and social consequences. Yet, much less is known about the amount of biodiversity loss directly resulting from the use of military technology. This paper analyzes the environmental consequences of one of the largest aerial and naval conflicts of the late 20st century, namely the 1982 Falklands War. As an indicator of the marine ecosystem status, we analyze population trends of king penguins breeding on the Falkland Islands over the period 1963-1997. Using interrupted time series analysis, we find that the war significantly slowed the growth rate of king penguins' population. To take better account of time-varying confounders, we complement this analysis using a synthetic control group based on data from other Sub-Antarctic colonies and find similar results. .