In an incident in the Persian Gulf on Tuesday, an Iranian Revolutionary Guard ship sped toward a US destroyer, the USS Mahan, and reached within 1,000 yards of it before changing direction and sailing away. The Iranians were manning the weapons on the deck of their ship at the time of the incident. The crew of the Mahan ordered the Iranian ship by loudspeaker not to approach, sounded the ship's danger signal, fired flares and sent out warnings on the emergency radio frequencies used by all the vessels in the Gulf, but to no avail. A senior US officer later described the Iranian ship's action as "obviously provocative behavior". Iranian vessels carried out 35 provocative maneuvers against US ships in international waters during 2016, 50 percent more than they did the previous year.