The U.S. Navy officer was eager to talk.

He’d seen his ship, one of the Navy’s fleet of 11 minesweepers, sidelined by repairs and maintenance for more than 20 months. Once the ship, based in Japan, returned to action, its crew was only able to conduct its most essential training — how to identify and defuse underwater mines — for fewer than 10 days the entire next year. During those training missions, the officer said, the crew found it hard to trust the ship’s faulty navigation system: It ran on Windows 2000.

The officer, hoping that by speaking out he could provoke needed change, wound up delaying the scheduled interview. He apologized. His ship had broken down again.

“We are essentially the ships that the Navy forgot,” he said of the minesweepers.

Thousands of miles away in the Persian Gulf, another officer, this one assigned to a minesweeper in the Navy’s 5th Fleet, offered much the same account. While tensions with Iran seem to escalate by the day, the officer said the four minesweepers based in the Gulf were so physically unreliable that he doubted his superiors would actually send them into action in a crisis.

The ships are one of the Navy’s primary tools for finding and neutralizing mines. They use sonar to hunt for them. The bombs are then disabled by divers, underwater drones or towing equipment dragged behind the stern.

But the aging minesweepers routinely need repairs, the officer in the Persian Gulf said, and the companies that used to make a variety of spare parts no longer exist. A sailor recently aboard one ship said the sonar meant to detect mines was so imprecise that in training exercises it flagged dishwashers, crab traps and cars on the ocean floor as potential bombs.

Clearing mines from the Persian Gulf effectively would require multiple ships underway for a sustained period. A Navy spokesman acknowledged that the service has struggled to put a “fully mission-capable” squad to sea. Only a quarter of the time over the last year did more than one ship meet that definition — although he said the ships could still be sent out.

“We are eager to operate if called upon,” the officer aboard one of the Persian Gulf ships said. “We’ll operate the systems as best as they can operate. My concern is the ships are old and, like any old ship, they break.”

The Avenger-class ships were built in the late 1980s and early ’90s and slated for retirement years ago. But their retirement date has been continually delayed because the service still doesn’t have a working replacement. The Navy’s latest estimate is that the ships will all be decommissioned by fiscal year 2023.

Senior Navy officials have called their mine warfare fleet in the Persian Gulf — a mix of aging ships, high-tech drones and helicopters — “the best and the brightest around,” and a Navy spokesman recently said the minesweeper fleet was “fully capable” of fulfilling its mission of finding and neutralizing mines. The Navy’s underwater drones, the spokesman said, “have a high rate of success,” and the sonar systems on the ships “are very accurate at detecting mines.”

While the spokesman conceded “there are challenges with all older ships, including maintenance and repair” that might make it take longer for the ships to accomplish their mission, he said maintenance problems have “dramatically improved” of late. He noted that as recently as July 6, all four of the older minesweepers based in the Persian Gulf had been at sea at the same time. (An officer aboard one of the ships called it a “photo exercise” and said it was “extraordinarily rare” to see all four out at once.)

ProPublica has spent this year examining the Navy’s state of readiness, including its response to known vulnerabilities in its ranks and arsenal. As part of that effort, ProPublica spoke with a dozen Navy officers, sailors, contractors and experts about the mine warfare unit. Those interviewed asked for anonymity so they could candidly discuss what they allege is neglect in the unit. The weakness they describe is in a relatively modest and unglamorous division of the Navy — 11 ships with a limited mission — but they nonetheless feel the problems have become more pressing given the United States’ volatile relationships with Iran and North Korea.

Those interviewed said Navy brass had made damaging budget decisions that have kept them from having a well-functioning mine warfare fleet.

“It’s not that they don’t want it, it’s that they want other things more,” one officer said. “Every dollar you’re spending on [mine countermeasures] is a dollar you’re not spending on some cool new submarine.”

To make matters worse, efforts to replace the aging ships with newer ones have met with repeated costly delays. And the quality of the training given to the sailors in the unit had suffered.

A defense contractor who has worked with the ships in recent years said the minesweepers suffered the highest rate of mechanical problems of any Navy ship. (A Navy spokesman declined to comment on that assessment, but he said that “recent metrics show that there has been substantial improvement.”) The USS Devastator, or MCM 6, was recently out of commission because the Navy couldn’t fix a key part, according to a sailor who recently served a long tour on the ship. The ship was out of the water so long the sailors started jokingly referring to it as “Building 6,” since it never actually moved.

Another military contractor who has worked with the minesweepers said the Navy has historically relied too heavily on computer-based training instead of hands-on exercises. Sailors on the ships, he said, often do not know how to use their equipment.

“I’m telling you they can’t do it, not with any degree of operational proficiency,” the contractor said.

The Navy built its first modern minesweeper during the 1940s. The fleet proved critical during World War II for clearing heavily mined waters in the Pacific for warships to pass and ahead of large amphibious assaults, such as the war-defining Battle of Okinawa. Some of those ships were then recommissioned to do the same job during the Korean War after hundreds of Soviet-made mines were dropped by the North Koreans.

Decades later, the Korea-era ships were part of an international effort led by the British in the Persian Gulf to try to keep the shipping lanes safe during the mining campaigns of the Iran-Iraq War. And then again in 1991, those old minesweepers, along with the first commissioned Avenger ship, were in the same waters struggling to clear a path for U.S. warships to approach the coast of Kuwait during the Persian Gulf War. Two U.S. vessels had been damaged by mines. After the war ended, the minesweeper units trolled the waters off Kuwait to find and disarm the more than 1,000 mines Iraq had dropped in concentric arcs for miles.

As the rest of the new class of minesweepers were commissioned, they deployed to the region and became a regular fixture there. The Avenger-class ships were called into service during the 2003 invasion of Iraq to stand ready for any mining near an Iraqi port that would be key for getting supplies and humanitarian aid into the country during the war.

Iran, which is also believed to have thousands of naval mines, has stepped up its aggressiveness in the Persian Gulf in recent weeks.

The mines are dropped into the sea and explode when ships pass. Iran’s arsenal includes a mix of cheaper, older ones that float and blow up on impact, and more sophisticated ones that can be dropped from planes. They sit on the ocean floor and explode after detecting nearby ships.

“We certainly have the ability to do it,” Iran’s foreign minister, Mohammad Javad Zarif, said last month about closing the Strait of Hormuz, a critical commercial passageway. “But we certainly don’t want to do it because the Strait of Hormuz and the Persian Gulf are our lifeline.”

Sailors in the 5th Fleet’s minesweeping operations said they have watched the escalation of hostility in the Persian Gulf — the downing of drones by Iran and the U.S., masked gunmen rappelling from an Iranian helicopter to seize a British-flagged oil tanker — with a mix of excitement and pessimism. They are eager to contribute but doubt their ability to do so.

Asked if the ships could effectively find and remove mines in the Gulf if they had to, one officer was blunt: “No.”

The Bahrain-based minesweepers, more than two times the length of a basketball court, are made of wood so they can more safely approach magnetic naval mines. Sailors have to be cautious about bringing anything made of metal on board, mindful even of where they store canned foods.

Like all ships deployed abroad, the minesweepers operate on a cycle: a planned ship maintenance phase, followed by basic training when the crew practices finding and disarming dummy mines, and finally underway periods, which include shows of force and joint exercises with allied navies. Those interviewed said the four ships do receive all of their allotted maintenance time, but the ships frequently require their crews to cannibalize working parts from other minesweepers — a challenge considering how few of them there are — or wait for new replacements.

“It takes a long time,” one officer said. “Many, many months.”

As a result, the officer said each of the four ships are typically underway only 15% of the time. Sometimes, those interviewed said, the training missions that get done prove as frustrating as being stuck in drydock. The sailor who’d been on the Devastator said the underwater drones are successful in finding mines only about 20% of the time. He knew of only one time when the crew was able to find a mine, and that was during a training exercise when it had the GPS coordinates for it.

“We joke about it all the time,” said the officer who is based in Japan. “It seems like somebody’s doing a social experiment. They take 80 or 90 well-intentioned, talented or motivated people and put us on ship with broken and unreliable equipment and give them an impossible task and see how they handle it mentally and emotionally.”

That there are problems with the mine warfare unit is well known to the Navy.

The Navy’s former top officer, Adm. Jonathan Greenert, told ProPublica that when he took command in 2011, he was immediately notified of the deteriorating mine warfare units in the Persian Gulf by the combatant commander in the Middle East at the time, Gen. Jim Mattis.

Greenert said he responded by putting more of an emphasis on the use of newly developed unmanned vehicles that could be dispatched to find and detonate mines. And he ramped up mine-clearing exercises with other navies, including those of the British and Gulf states.

The effort didn’t resolve some of the unit’s issues, however.

In 2013, the USS Guardian, a minesweeper, accidentally ran into a sensitive coral reef in the Philippines. No one was injured, but the $212 million ship had to be decommissioned, and the U.S. ambassador was forced to apologize for the damage to the World Heritage site.

Three years later, the Navy’s Sea Dragon helicopters, which stream cables that dislodge mines moored to the ocean floor, came under damning scrutiny. In a lengthy examination in The Virginian-Pilot, the Sea Dragons were found to have been used long after they were supposed to be retired. Over a three-year period, they had crashed at a higher rate than any other military aircraft, including a 2014 crash that killed three service members.

The Navy’s plan to replace the minesweepers with a new class of vessels, known as Littoral Combat Ships, has been repeatedly delayed by cost overruns and technical deficiencies. The push to develop the new line of ships has been a financial drain on the minesweeping budget and the maintenance of the existing fleet.

Congress, concerned about resources being diverted, has required the Navy not to decommission the ships or reduce how many sailors are assigned to them until there’s a replacement that would “meet or exceed” their capabilities. The Navy, in the shipbuilding plan it submitted to Congress this year, said that in the next year it would begin retiring three of its 11 minesweepers — the ones based in the U.S., in San Diego — and harvest their parts to service the eight ships based in Japan and Bahrain.

An officer briefed on the planning said top Navy officials were reluctant to pump more money into maintaining the older minesweepers and were taking a gamble that the new ships would finally be ready just as the legacy minesweepers were decommissioned.

“We’d be extremely lucky if those lined up,” the officer said. “There has been a conscious decision by Navy leadership to assume risk in the present.”

Asked whether the Navy was taking a risk assuming the new line of ships would be ready to take over before the Avengers were decommissioned, the Navy’s spokesman would only say that the Navy is constantly reviewing its capacity for the mission.

In the Persian Gulf now, one officer described the difficulties of instilling a sense of urgency and mission in sailors who doubt the senior ranks of the Navy will ever trust their prowess if Iran were to deploy mines.

“I have to tell them, ‘We always have to be ready,’” the officer said. “But it is tough to put your people through very hard conditions when you privately think you’re not going to go out.”