On Monday, projectiles launched by Iran struck two vessels owned by the Greek firm Dynacom as they passed through the strait, part of an escalation of reciprocal strikes that has reduced tanker traffic to a trickle after a brief resurgence in the past month. As tanker traffic pulls back and crude prices rise, “the premium now from just being able to sell cargoes can’t be overstated,” said Ian Ralby, senior security fellow at the Center for Maritime Strategy, a think tank. But for shippers, the risks are also rising: A third Dynacom tanker was struck on Monday by a Ukrainian drone in the Black Sea as it loaded oil from a Russian port. And new threats by Houthi militias in Yemen to attack tankers exiting the Red Sea could open another hostile front. “This is going to become dicey, and a lot of shipowners will sit on their hands,” Ralby said.