Final answer:
Paraguay suffered the loss of 70% of its male population in the War of the Triple Alliance, fought against Brazil, Argentina, and Uruguay from 1864 to 1870.
Step-by-step explanation:
The country that experienced the catastrophic loss of 70% of its male population in the War of the Triple Alliance was Paraguay. This conflict, which occurred from 1864 to 1870, was fought between Paraguay and the allied forces of Brazil, Argentina, and Uruguay. The war was incredibly devastating for Paraguay, not only in terms of the loss of life but also with regard to its economy and territorial integrity. Estimates suggest that the war resulted in a massive demographic imbalance due to the significant male population decline. In the aftermath, Paraguay faced a long road to recovery, with many challenges in reshaping its society and future prospects.