The US is enforcing the blockade the way it enforced the last one: Putting mainly shipping vessels on the route, and predominantly the route that runs close to the Iranian coast, to prevent any vessels associated with Iran from leaving via that route.
Now, it appears to be adopting both the blockade, as well as protection of the other routes through the Strait of Hormuz, that is the one that hugs the coast of Oman.
The US says it will protect shipping that goes along that route. Iran continues to insist that it will continue to attack shipping that goes along that route.
So we are seeing this come into force now. And just an hour before that, we heard from CENTCOM that a fourth round of strikes has been launched.
So you now have a fourth round of strikes being carried out by CENTCOM, it says, on targets associated with Iranian action in the Strait of Hormuz.