Iran could do this by attacking ships in the Strait, scuttling its own ships, laying mines or just threatening to launch Silkworm anti-ship missiles at any passing tanker.
The U.S. Navy will be forced to break the blockade. We will succeed but at considerable cost. And it will take time -- during which time the world economy will be in a deep spiral."
This surprises me, because I thought that Krauthammer was smarter than this. Does he really think the US Navy will be in react mode in the Strait of Hormuz, waiting for the Iranians to start causing havoc before they do anything to "break the blockade"? I can't imagine the Navy doing anything other than preventing a blockade and securing the Strait for the 15 minutes or so that it will take to crush the Iranian Navy and every known and suspected threat along the Iranian coast.
Back up. Go back to the first paragraph, "closing the port," and keep in mind that there are trade agreements being broken here. If ships are attacked, it's an act of war, as well. Does it still sound stupid?