호르무즈 해협을 통한 선박 운항의 위험

Controllers for shipping companies face a daunting decision as they try to free vessels trapped in the Persian Gulf: “Basically you’re sending someone unarmed into war.”

Silke Lehmköster oversees 310 vessels as the fleet managing director at Hapag-Lloyd, a shipping giant in Hamburg, Germany.Credit...Maximilian Mann for The New York Times

Reporting from Hamburg, Germany

Capt. Silke Lehmköster, from her office overlooking the Alster River in Hamburg, Germany, wrestles with the same question every day: Is it finally safe for her to order five of the container ships she oversees, which have been stranded in the Persian Gulf, to exit via the Strait of Hormuz?

For nearly two months, the answer was “no.” Then, early this week, she saw a window of opportunity and gave one of the vessels the green light to cross the strait.

On Monday, just before midnight, under a new moon and with hardly any wind, one of her ships, the Tema Express, crossed the strait without incident. The ship, which then anchored off the coast of Oman, near Muscat, was the company’s first to pass through the waterway since the start of the war.

Other commercial vessels that tried the crossing soon after were not so lucky. Two European-owned vessels were intercepted and seized by Iranian forces on Wednesday, one attacked by a gunboat without warning. They are being held near Iran’s coast.

More than 20 commercial ships have come under attack around the strait since March. The attacks started shortly after the first strikes on Iran by the United States and Israel, which prompted the Iranian military to retaliate by throttling traffic through the vital waterway.

The strikes have killed 10 seafarers and injured many others. With shipping companies reluctant to navigate such treacherous waters, roughly 20,000 crew members aboard some 1,600 vessels have been stranded in and around the strait, where about one-fifth of the world’s oil had passed before the war.

On Thursday morning, Captain Lehmköster, who oversees 310 vessels as the fleet managing director at the shipping giant Hapag-Lloyd, assessed official advisory notices, liaised with intelligence sources and communicated with seafarers.

As reports continued to trickle in about the two seized vessels, senior leaders discussed the escalating risks for the company’s ships still stuck near the strait. The vessels that were targeted on Wednesday were the first commercial ships that Iran had seized since the war started.

Over the past week, the U.S. Navy has boarded and taken control of Iranian-flagged ships in the Arabian Sea and Indian Ocean. On Thursday, President Trump said he had ordered the Navy to shoot any boats laying mines in the Strait of Hormuz.

At Hapag-Lloyd’s six-story headquarters in Hamburg, workers speak a mix of English and German in the hallways, which feature reminders of the company’s long history, including a nine-foot-long model of the Imperator, a steamer that launched in 1912. The building sits on the grand Ballindamm boulevard, named after the German-Jewish shipping magnate Albert Ballin, who in the late 1800s and early 1900s helped build what is now known as Hapag-Lloyd into a global conglomerate. Today, the company is the fifth-largest container shipping group in the world.

In the company’s operations room on the ground floor, workers monitored weather patterns at their computers and kept an eye on traffic in the Strait of Hormuz on a giant screen where vessels were tracked in real time. Similar control centers are at other shipping companies around the world, with most of the globe-spanning industry’s attention gripped by that single strait, a choke point whose influence over the global economy has become alarmingly clear.

Captain Lehmköster said she would need clear guarantees from both the United States and Iran that passage was safe and details about how to avoid the naval mines planted in the strait before giving orders for the other four ships to proceed. These assurances have not come.

“Basically you’re sending someone unarmed into war,” Captain Lehmköster said in an interview, noting that the stranded ships have no ability to defend themselves.

Captain Lehmköster declined to comment on the route that the Tema Express had taken to cross the strait. Industry analysts suggest that it most likely took a route that hugged Oman’s coast, a path some vessels have taken to cross without permission from Iranian officials, who have enacted increasingly strict controls over the strait.

For Captain Lehmköster, 39, who herself worked at sea for 15 years, the decision of whether it is worth the risk to dispatch a vessel through the strait is personal and the responsibility of overseeing ships stranded in a war zone weighed heavily.

On board the four stranded Hapag-Lloyd ships are roughly 100 seafarers — Ukrainians, Russians, Vietnamese, Sri Lankans, Romanians, Filipinos and others — all desperate to get home, she said.

Staying put can also be risky. Several weeks ago, the crew on a Hapag-Lloyd ship awoke in the early morning hours to fire alarms, after shrapnel from an Iranian missile or drone fell on their ship, starting a fire. Nobody was injured, and the ship is in repair, able to maneuver but with difficulty.

Ship captains are trying to keep seafarers’ spirits up with activities like barbecues, foosball tournaments, and karaoke and movie nights. They are maintaining the usual shifts for maintenance, lookouts and checks on cargo, which typically includes furniture, electronics, fruit, and frozen fish and meat.

Mixed messages from the American and Iranian authorities, who have imposed competing blockades and restrictions on traffic in the gulf, have made it difficult to gauge the risks of transiting the strait, especially from afar. During an uneasy cease-fire, now entering its third week, the strait has been declared open one moment and closed the next.

In addition to Hapag-Lloyd, other major shipping groups, like CMA CGM of France and MSC of Switzerland, have moved some ships through the strait in recent days. The ships the Iranians seized this week were owned or operated by MSC.

The Danish shipping giant Maersk, which has seven ships stranded in the region, has deemed conditions too unsafe for ships to transit.

For some companies, the economic payoff — especially as oil, gas and other commodity prices have surged — is worth the risk. “Typically, if you are successful, you get a big reward,” said Jakob P. Larsen, the chief security officer at BIMCO, the world’s largest shipping association.

Even in more peaceful times, the hourslong voyage through the Strait of Hormuz can be hair-raising.

It is narrow — 21 nautical miles wide at its narrowest — with dense traffic. Captains must navigate around small fishing vessels and oil rigs. The air is often hazy because of the heat.

Capt. Alexander Meier, 48, who most recently steered ships through the strait for Hapag-Lloyd three years ago, tries to project a sense of calm to his crews while transiting past Iran, he said.

“The captain should never be nervous,” he said. But he always breathes a sigh of relief when he gets through. “There is always some tension if you pass there,” he said.

Charalampos Kiakotos, a ship captain who has also navigated the strait more than a dozen times, said it was among the most demanding passages. The risk of being stranded in a war zone would be especially stressful, he said in a call from the Port of Dos Bocas in Mexico, because of the pressure to follow directions from the head office to transit as quickly as possible, while also looking out for crew members.

“If anything happens, everyone will blame the captain, and they will say it was the captain’s decision,” said Captain Kiakotos, 45, who works for a Greek shipping company. “So at the end of the day, I will have the final decision.”

Among the most difficult aspects for the seafarers around the strait is the uncertainty about when the standoff will end, said Captain Lehmköster in Hamburg.

“What does the Filipino seafarer aboard one of our vessels have to do with the problems that Israel, Iran and the United States have with each other?” she said. “They are there to earn money to feed their families.”

Adina Renner contributed reporting from London.

An earlier version of this article misidentified the waterway that the shipping giant Hapag-Lloyd’s office overlooks. It is the Alster River, not the Elbe River, into which the Alster flows.

When we learn of a mistake, we acknowledge it with a correction. If you spot an error, please let us know at corrections@nytimes.com.Learn more

Jenny Gross is a reporter for The Times covering breaking news and other topics.