The UK Maritime Trade Operations Centre confirmed Monday that a vessel was struck by unknown projectiles in the Strait of Hormuz, hours after President Trump announced the U.S. would begin guiding ships through the waterway with military support. The word “unknown” is doing significant work in that sentence. In a strait where Iranian forces have been operating against commercial shipping, where the U.S. military has active minesweeping operations underway, and where the IRGC has demonstrated both the capability and the willingness to attack vessels under ambiguous conditions, “unknown” does not mean the intelligence community has no candidates. It means the attribution has not reached the threshold for public declaration.

As of Monday, the United States announced it would begin guiding ships through the Strait of Hormuz with the support of guided-missile destroyers, more than 100 aircraft, and 15,000 service members. A tanker was struck by unknown projectiles in the strait within hours of the announcement. The dual blockade — the U.S. Navy preventing access to Iranian ports while Iran restricts commercial shipping through the strait — has now entered a phase where each side is testing the other’s escalation threshold in a waterway that carries roughly one-fifth of daily global oil production.