But no one should expect Iran to stop its provocations, especially as it concludes there is little cost to escalating. The weekend aggression comes after Mr. Trump called off an airstrike in June to retaliate for the shooting down of a $130 million U.S. surveillance drone. On Twitter on Tuesday, Senator Lindsey Graham said the weekend attacks show that Iran sees Mr. Trump’s cancellation of the strike as “a sign of weakness.”

The President shot back that it was a sign of strength that “some people just don’t understand.” But the facts are on Mr. Graham’s side. Mr. Trump has loudly made clear he is reluctant to pursue the military option, and in the Middle East adversaries respect only strength. The U.S. and Saudis have shown they can’t protect the oil fields, and the next attack may hit the United Arab Emirates or Kuwait…

Mr. Trump wants to reduce every foreign controversy to a negotiation with some head of state, and the world’s bad actors are figuring that out. Tehran has a clear policy to become the dominant power in the Middle East, and its actions—including aggression to destabilize its Arab neighbors—support that policy. Mr. Trump had better prepare for more Iranian trouble.