WARSAW, Poland — For decades, borders seeded with antipersonnel mines divided the Soviet bloc from the West, deterring citizens from fleeing across the Iron Curtain.

At the end of the Cold War, the mines were painstakingly dug up along the long frontier of the collapsed bloc. Anti-mine campaigners, helped in their cause by Diana, Princess of Wales, pushed world leaders to hammer out a global treaty banning a deadly weapon that indiscriminately kills civilians.

Now, in yet another consequence of Moscow’s 2022 full-scale invasion of Ukraine, five countries bordering Russia plan to revive the use of a weapon prohibited by most countries for more than a quarter of a century, hoping to strengthen their defenses against Russian attack.

Recent moves by Poland, the three Baltic states and Finland — and a vow by President Volodymyr Zelenskyy of Ukraine — to quit a mine ban treaty that came into force in 1999 won’t result in any immediate surge in the use of antipersonnel mines. Formally leaving the treaty is a six-month process.

But the recent rush of countries rejecting a pillar of the post-Cold War order has outraged anti-mine campaigners.

“We are furious with these countries,” said Tamar Gabelnick, director of the International Campaign to Ban Landmines, which in 1997 won a Nobel Peace Prize for its work clearing antipersonnel weapons and its role as the driving force behind the Mine Ban Treaty, known as the Ottawa Convention.

“They know full well that this will do nothing to help them against Russia,” Gabelnick said, dismissing a retreat from the global accord as “just political games” by officials trying to present themselves as defenders of national security. Senior military officials in at least three of the five countries whose parliaments recently voted to withdraw from the treaty have said in the past that they saw little military utility in reviving antipersonnel mines. The weapons mostly kill civilians and offer limited defense against modern mechanized armies.

The war in Ukraine “changed everything,” said Veronika Honkasalo, a left-wing member of the Finnish parliament who is opposed to leaving the treaty, a move supported by an overwhelming majority of her fellow legislators in a recent vote. Because of Russia’s invasion of Ukraine, she added, “people got really scared because we have a 1,300-kilometer border with Russia and long history of war with our neighbor.”

Of the European countries that share a land border with Russia, only Norway has stayed steadfast in its commitment to the Mine Ban Treaty.

The treaty, according to the United Nations, led to the destruction of more than 55 million antipersonnel mines. The weapons were widely used in the Cold War era, in conflicts in Afghanistan, Angola, Cambodia, Myanmar and many other countries, but continued to kill people long after fighting ended. Eighty percent of the casualties from antipersonnel mines are civilians, many of them children, according to the International Committee of the Red Cross, which estimates that the number of people killed or maimed each year has fallen to around 3,500 from more than 20,000 over the last two decades.

“It is a horrible weapon,” Honkasalo said.

Public awareness in the West of the dangers posed by the mines rose sharply in the 1990s, in part as a result of Princess Diana’s support for campaigners. Diana, said Paul Heslop, a British mine clearance expert who escorted her on a visit to a minefield in Angola in 1997, “would be very disappointed that 28 years after her visit, and all the progress that been made since, that the world is taking a step backward.”

But “she would ask why this is happening,” added Heslop, who is the senior mine action adviser to the United Nations in Kyiv, Ukraine. The Ottawa Convention, he said, “would be completely intact if there had not been a war in Ukraine.”