New Delhi, May 22 -- Iranian Revolutionary Guard members now regularly show the public in Tehran how to handle Kalashnikov-style assault rifles. Parades through the capital feature military vehicles mounted with belt-fed Soviet-era machine guns. And at one mass wedding, a ballistic missile, like the one that rained down cluster munitions on Israel, adorned the stage.

Weapons are now regularly brandished in Tehran, an increasing show of defiance as U.S. President Donald Trump threatens he could restart the war with Iran should negotiations break down and the Islamic Republic refuses to release its grip on the Strait of Hormuz.

The weapons displays reflect the genuine threat Iran faces: Trump has suggested American forces could seize Iran...