War of the Triple Alliance
ND – MPE: 0.21
The Wikipedia article called “Paraguayan War” cites 0.44 million as the best estimate for the total number of deaths from 1864 to 1870 – 63000 Brazilian and Argentinian civilians, 300000 Paraguayan soldiers and civilians. All these numbers could be far too low. Plausible estimates for the total number of civilians killed in the war range from 0.1 to 0.35 million. I choose 0.21 million as the most plausible estimate.