For months, the U.S. military has sought to protect tankers from Iranian attacks as they carry Persian Gulf oil through the Strait of Hormuz. But last week, a Saudi vessel trying to go through the strait was struck close to Oman’s coast, killing two of its crew members. Two other sailors died in attacks in August, making it the deadliest month in the strait for merchant seamen since March. At least 23 ships were hit in the waterway in July and August. On Saturday, the United States struck three Iranian oil tankers in retaliation for what it said were unprovoked attempts by Iran to attack two U.S. warships. After more than six months of war, analysts said the strait remained in a lethal stalemate. "The strait is neither fully closed nor fully opened," said Eugene Gholz, an associate professor of political science at the University of Notre Dame and an expert on conflict in the waterway. "Iran can't close it completely, and the U.S. can't open it completely."

The U.S. tanker protection effort, which involves intercepting Iranian drones and missiles before they hit ships, has helped get millions of barrels of oil out of the Persian Gulf each day and provided a measure of relief to oil markets. But attacks from Iran have continued to deter many tankers from operating in the strait. Despite the U.S. protection, Iran has managed to keep hitting vessels. Iran struck 12 ships in August, up slightly from 11 in July, according to a New York Times analysis of public attack records. The amount of oil going through the waterway is still significantly lower than it was before the war, analysts said. In the seven days through Thursday, a daily average of 6.7 million barrels of oil transited the strait, nearly 60 percent less than in the months before the war began at the end of February, according to Tanker Trackers.com, a maritime analysis firm.

Iran has used its ability to scare ships away from the strait — and restrict the supply of oil — as leverage against the United States. Iran now wants to formalize its influence over the waterway by charging ships fees for using the strait, something the United States opposes. And despite the U.S. military's efforts to fend off Iran's attacks on tankers, many private shipping companies have not returned to the Gulf. Industry executives said they didn't want to risk the lives of their crews or lose a vessel for weeks if it was struck.