In the last hours of the 1991 Persian Gulf War, U.S. forces encountered a problem of the Pentagon’s making: They had surged toward Iraqi positions so quickly that they were encountering their own land mines dropped from friendly aircraft.

“Due to rapid Allied advance, activated Gator minefields could be encountered,” read an Army advisory on Feb. 28, referring to anti-personnel and antitank mines. “Extreme caution must be exercised in moving/maneuvering through areas where air strikes have been conducted.”

Since then, most of the world — the United States being an exception — has banned the production and use of land mines because of their threat to civilians long after wars end.

So the Trump administration’s decision this week to expand the use of land mines has baffled and angered humans rights and arms control groups, which say the decision further imperils anyone who may encounter the weapons.

“It’s incredibly troubling we’re having such a step back in acceptable international norms,” Rachel Stohl, an arms control expert at the Stimson Center, a nonpartisan policy research center, told The Washington Post on Saturday. “This is one of the most inhumane weapons that we know of.”

“It’s a potential humanitarian catastrophe” to use them again, she added.

In 2018, nearly 20 civilians were killed or injured every day by land mines and other unexploded ordnance remnants, such as cluster munitions, according to the International Coalition to Ban Landmines. That is almost certainly a conservative number. Children represented 40 percent of the casualties, the group reported.

What are land mines, and what has changed?

The new policy affects anti-personnel land mines, which are small explosive charges buried in or placed on the ground.

They are designed to kill and injure enemy forces. Tactically, they are used to delay enemy troop movement or force combatants to take another path. That makes their movement more predictable and can help U.S. forces target them more easily.

But they remain where they were placed and often kill, maim and blind civilians years or even decades later.

“War surgeons consider [mines] among the worst injuries they have to treat,” the International Committee of the Red Cross has said.

Land mine use and production are banned by 164 countries. The United States is not one of them, but Obama-era restrictions only allowed anti-personnel land mines to be used in defense of the Korean Peninsula and called for destroying stockpiles that were not meant for that defense. The new Trump policy reverses those regulations.

Most land mines that menace civilians are “dumb” or persistent, meaning they are built with mechanical fuses and are triggered by the victim with no other safeguards. They can remain dangerous indefinitely until someone — commonly a child or farmer — encounters one in the dirt. The United States does not have any of these land mines in its inventory, defense officials said.

In recent decades, the United States has produced “smart” or nonpersistent mines that can be set to self-destruct in a certain number of minutes, hours or days after they are deployed.

Are land mines really safer now?

The capability of nonpersistent mines was championed by the Pentagon on Friday when it defended the policy change, with one official claiming a “6-in-1 million chance of a U.S. land mine being active after a pre-determined period.”

Nonpersistent mines would lead to a lower risk of harm to civilians, the Pentagon said, but the agency did not respond to a follow-up question asking how that number was calculated.

Experts second-guessed that confidence and have rejected the notion of a “smart” mine as risk-free or danger-free to civilians.

“Like any microchip-based electronic device, there are going to be failures,” said Mark Hiznay, the associate arms director for Humans Rights Watch. Hiznay speculated that the Pentagon estimate was conjured by calculating electrical component failure rates, not actual mine deployment studies.

Other evidence points to an imperfect weapon that posed a danger to U.S. troops.

Nearly 120,000 “smart,” nonpersistent mines were used in the Gulf War, which was the last time the United States used land mines in warfare outside a single use in Afghanistan in 2002. Even though the Pentagon suggested a low dud rate, anti-personnel and antitank weapons that failed to self-detonate littered Kuwait, a 2002 Government Accountability Office report said.

Nearly 2,000 duds were uncovered by contractors working in one sector alone out of seven, the GAO report concluded.

“Every dud is dangerous,” Hiznay said.

And because of uneven and chaotic battlefield reporting, it is possible some U.S. casualties attributed to enemy land mines and explosives were caused by these munitions, the GAO report said.

Newer land mines were developed to mitigate future harm to civilians. The Spider Networked Munition, for instance, includes a “human in the loop” that allows troops to trigger the explosives and show locations on GPS.

But it is unclear if the land mines the Pentagon has authorized for use will include such an oversight ability. The agency did not address a question about that capability.

What does this mean for civilians and the future of war?

Pentagon officials have said commanders need the option to use anti-personnel mines to take on conventional adversaries such as China and Russia.

But one problem that may arise: All NATO partners of the United States have signed onto the ban, potentially creating problems in theoretical coalition missions, said Stohl of the Stimson Center.

And future battlefields may be so dynamic that the mines might not disarm in time before they harm whoever is nearby.

“When it’s active, it’s not distinguishing between a civilian and a legitimate target,” Stohl said.

That alarm has been sounded by commanders for decades.

‘‘What the hell is the use of sowing [anti-personnel mines] if you’re going to move through it next week or next month?” former Marine Corps Commandant Gen. Alfred M. Gray Jr. said in 1993.

The Pentagon’s embrace of land mines also puts it at odds with a key diplomatic State Department program, which has worked to find and destroy remnant explosives in 100 countries since 1993 — a $3.4 billion effort.

But it’s clear that civilians worldwide will be haunted by the threat under their feet for decades to come.

In Vietnam alone, leftover land mines and other explosives dropped by the United States have killed 40,000 people since the end of the war, and it may take 300 years for all remaining munitions to be cleared.

In other words, the last Vietnamese person to be killed by an unexploded U.S. munition probably hasn’t even been born.

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