Five Iranian patrol boats — likely those of the Iranian Revolutionary Guard — intercepted, fired toward, and then boarded a cargo ship, the Danish-owned MV Maersk Tigris, early this morning, the Pentagon has confirmed. Although the Pentagon notes the ship has no Americans aboard, and flies the Marshall Islands flag, all security and defense responsibilities of the Marshall Islands, as Tom Rogan pointed out to me, are handled by the U.S. government.

What exactly this means for U.S. obligations in this case isn’t entirely clear, but the Marshall Islands representative to the U.S. tells Bloomberg View that he believes the country has no practical or legal ability to help the ship, and that that falls to the U.S.

An American destroyer, the USS Farragut, headed for the scene as soon as the distress call was heard, but didn’t get there before the ship was in Iranian custody. The Iranian government says the Tigris was in Iranian waters, inside the Strait of Hormuz. According to a ship-tracking website, the ship was headed into the Persian Gulf, headed for a port in the United Arab Emirates.

Tensions have risen between U.S. and Iranian naval forces in the last couple weeks: The U.S. beefed up forces in the region recently, suggesting that it might try to block Iranian shipments of supplies to rebels in Yemen fighting the U.S. backed government there, but the U.S. then backed off of the possibility, saying it had no intentions of blocking Iranian traffic.

If Iran wants to try telling the U.S. to stay out of this situation, seizing a ship for which the U.S. seems to have some responsibility, but without taking any American citizens, seems like a crafty way to, shall we say, test the waters . . .

UPDATE: Meanwhile, in Yemen itself: