The United States reportedly is planning to deploy Marines aboard commercial vessels in vital Middle Eastern waterways amid Tehran’s escalating maritime aggression in the area, including recent drills by Iranian naval forces on and around contested islands near the Strait of Hormuz. The lack of credible U.S. deterrence thus far has emboldened Iran to increase its naval harassment in the region and led U.S. partners to rethink their cooperation with the United States over concerns that Washington is not committed to upholding regional stability. The move to protect commercial ships, if implemented with a clear willingness to use force when necessary, together with other recent enhancements to U.S. force posture around the Gulf, are important and much-needed steps by the Biden administration to address Iran’s threats to global commerce and vital U.S. security partners. Given the history of Iran’s aggression, Tehran is likely to conduct further attacks to test the seriousness of this U.S. commitment. The United States must be prepared to respond forcefully against likely further Iranian provocations while also working concertedly with regional partners to improve and integrate their own maritime security capabilities.