Secretary of State Mike Pompeo on Thursday charged Iran with responsibility for the attack earlier in the day on two oil tankers in the Gulf of Oman. Mr. Pompeo cited intelligence reports and the nature of the weapons used, most likely torpedoes, as evidence. It is almost certainly true that Iran is behind the attacks, which makes it all the more important that the West unite in opposition to Iran’s aggression.

This was a sophisticated attack that only a nation with a sophisticated military could carry out. Within about...