The United States imposed its own naval blockade on Monday to block all traffic to and from Iran’s ports, and by Tuesday more than 12 American military vessels were stationed in international waters in the Gulf of Oman. The move has already been felt in the Strait of Hormuz, where a Chinese tanker called the Rich Starry was spotted heading east toward open water before making a U-turn.
Since the blockade took effect, no ships linked to Iran have been seen leaving the region, according to Kpler, and at least two vessels tied to Iran and under U.S. sanctions appeared to turn back toward the Persian Gulf by Wednesday. Some ships with no known link to Iran still passed through the strait on Monday and Tuesday, but they stayed close to the Omani coast.
The slowdown did not begin with the blockade. Vessel traffic in the strait eased almost immediately after the United States and Israel attacked Iran on Feb. 28, falling from around 130 ships a day to just a handful. At first, the few ships that crossed used the longstanding designated route through deep waters off Oman, but two weeks into the war, vessels began avoiding the official lanes and instead moved through shallower water near Iran.
That shift reflects the risk that has hung over one of the world’s most important chokepoints since the war began. Before the blockade, Iran allowed ships carrying its own cargo to pass through the strait even as it attacked commercial vessels and effectively halted shipping from almost everybody else. The United States had also previously let Iranian-linked oil tankers keep transiting the waterway to temper sharp increases in oil prices tied to the war.
Counting what is actually moving through the strait is difficult because vessels can hide or falsify location data, but the direction of travel is clear enough. Ships are hugging the Omani side, steering away from the center of the channel and from the possibility of sea mines, while the American military remains offshore and, as maritime analyst Jennifer Parker said, is likely watching from a distance with radar, patrol aircraft and drones.
For now, the blockade has turned Marine Traffic through the Strait of Hormuz into a test of who is willing to keep moving and who is willing to turn away.