Iran has long asserted that it can shut down the Strait of Hormuz. While the strait can't be "closed" in the traditional sense - like shutting a road - Iran could attempt to make the waterway too dangerous for commercial passage, effectively disrupting global shipping.

Pentagon officials are trying to prepare for all of the ways Iran could retaliate, as President Trump hints at what he might do.

Israeli aerial bombardment has wiped out much of Iran’s ballistic missile capability and decapitated its military command, but Supreme Leader Ali Khamenei has refused to stop fighting, even promising “irreparable damage” to the US if it intervenes in the conflict in support of its staunch ally.