Maybe throwing a third of your male population into a major war would qualify, but wars that major are quite rare.
They are now, anyway.
The Ottoman Empire lost 13-15% of its total population in WWI but had by far the worst proportional losses of that war, particularly from disease and starvation.
In WWII, Poland lost 16%, the Soviet Union lost 13%, and Germany 8-10%..
In the U.S. Civil War, the U.S. as a whole lost 3% of its population, including 6% of white Northern males and 18% of white Southern males..
Rare, not nonexistent. The World Wars are the main recent exception I was gesturing towards, although more extreme examples exist on a smaller scale: the Napoleonic Wars killed somewhere on the order of a third of French men eligible for recruitment, for example. And they were rarer before modern mass conscription, although exceptions did exist.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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