As it happens, today (April 14) marks 20 years since the USS Samuel B. Roberts hit an Iranian naval mine in the Persian Gulf. The mine, made to a Tsarist design from 1908, blew a truck-sized hole in the ship and set it on fire. No U.S. warship has come closer to sinking under hostile fire since the Korean War. Four days later, the U.S. retaliated with Operation Praying Mantis, which sank one Iranian warship and left another dead in the water, a loss that helped convinced Tehran to accept a ceasefire in the Iran-Iraq War.