For decades, Iran cultivated a myth of invincibility through terror and proxies—until war exposed the regime as weaker, poorer, and far more fragile than the world had feared. Until last year, for some 46 years, Iran enjoyed a North Korea-like reputation in the heart of the Middle East: always unpredictable, reckless, dangerous, inevitably to be nuclear, self-destructive, and nihilistic. All that said, was it really ever all that formidable? The mullahs came into power after the removal of the Shah and, subsequently, the interim secular socialists. They did so by taking American hostages, murdering opponents, executing former supporters, and transforming...