A small splash is being made by accounts of a recent Office of Naval Intelligence report claiming that Iran has achieved the capability of "easily" closing off the Straits of Hormuz in wartime. Supposedly, the Iranian navy has sufficient surface and subsurface vessels, along with advanced missile torpedoes, that can hold enemy naval ships at risk. This matters now because of concerns that an Israeli (or U.S.) attack on Iran's nuclear program could result in Tehran's retaliation, including choking off 40 percent of the world's oil supply.
Whether or not Iran truly maintains this capability--and it is hard to believe that even if Iran succeeded in closing off the Straits the U.S. Navy and Air Force would not be able to re-open them easily--any conflict in the Straits would prove to be the first test of the joint "Cooperative Strategy for 21st Century Seapower." Issued in October 2007, the Cooperative Strategy sought to provide an overall rationale for the use of U.S. naval assets, superseding the 1986 Maritime Strategy. The new strategy states that the U.S. Navy, Marine Corps, and Coast Guard will (among other goals) "secure strategic access and retain global freedom of action." This will be achieved through "regionally concentrated, forward-deployed task forces...continually postured in...the Arabian Gulf/Indian Ocean...." Among the rungs of operationalizing the maritime strategy is to maintain forward presence, to deter, and to achieve sea control. Each of these would come into play in a conflict in the Straits of Hormuz.
Given the emphasis the U.S. Navy puts on partnerships, goodwill missions, and the like--all of which are important--the ONI report on Iran's navy is notable for bringing back to the fore the traditional rationale for naval power: sea control. The Cooperative Strategy does not spend much time defining sea control, reducing it to "the ability to operate freely at sea," but it does explicitly state that "we will [not] permit an adversary to disrupt the global supply chain by attempting to block vital sea-lines of communication and commerce." Sea control would, in this rationale, be the prerequisite of "command of the sea," for that is what would ultimately keep the Straits open, while "sea control" would be the operational condition allowing U.S. naval forces to defeat the Iranians.