The commander of the Navy’s Fifth Fleet was in his office on the afternoon of July 25 when he got the phone call: An Iranian Navy frigate in the Gulf of Aden had approached a ship where an American military helicopter had just landed.

Crew members on the Iranian ship pointed a heavy machine gun at the American helicopter, an alarming provocation at a time when critics are trying to kill a nuclear deal limiting Iran’s nuclear program in exchange for sanctions relief. The American helicopter, following standing orders to defuse tensions instead of elevating them, took off from the ship, but the Iranian crew continued to track it with the gun for a few moments before turning away.

Then the report took a strange turn. During the entire episode, Vice Adm. John W. Miller, the Fifth Fleet commander, was told that an Iranian film crew aboard the frigate was videotaping everything. “The whole thing took a couple of minutes,” Admiral Miller said later, recounting his surprise at the film crew. “We have no idea why they were filming it.” […]