In the 1980s the Navy had to counter a broad effort by Revolutionary Guard forces, then at war with Iraq, to set mines and otherwise hamper and damage American-flagged oil carriers in the gulf. The conflict heated up in the summer of 1987, when an American-flagged tanker hit an Iranian mine. That fall, Army helicopters fired on and Seals boarded an Iranian ship laying mines in international waters. The Seals confirmed the presence of mines, detained the crew and scuttled the ship.

The following April, the frigate Samuel B. Roberts was blown nearly in half by an Iranian mine, leading American forces to retaliate by attacking two Iranian oil platforms that had been used as staging areas. The Navy destroyed nearly half the Iranian Navy and put a temporary end to the Revolutionary Guards’ waterborne presence.

Despite that humiliation, some in Tehran came away believing that a combination of mines, missiles and the fervor of the Revolutionary Guard members manning small boats could compete with the might of the United States Navy in the confined waters of the Persian Gulf. So, off and on for 20 years, the Iranians have been initiating small incidents, testing the limits of what America will accept.