Superlative form; most foolishly bold or reckless; showing the greatest degree of foolish daring without proper caution.
Superlative form of foolhardy, following standard English pattern. Foolhardy emerged in the 1500s and foolhardiest represents the extreme of this paradoxical boldness-meets-foolishness.
The superlative foolhardiest perfectly captures some of history's greatest disasters—it's the word historians use for decisions that seemed bold at the time but were actually dangerously uninformed, like Napoleon's invasion of Russia.
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