It depends on the objective of the war. Nation building is basically impossible. Killing the crap out of an enemy until they surrender is pretty effective historically. Killing the crap out of select targets while avoiding excessive civilian casualties is generally ineffective. WWII was a total war scenario, the US and USSR absolutely killed entire areas of German and Japanese towns.
Robert Evans has said several times in recent episodes of BtB that the mentality of “good at war means good at killing” is demonstrably false. The US and USSR won WWII not by being better killers but by taking and holding territory (and while awful being less awful than the Nazis.) The US has arguably lost all its conflicts since then because they fell in love with the idea that you can bomb or brutalize your way to victory.
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