After Britain leaves the European Union in 2019, the 310-mile border between Northern Ireland and Ireland will be the United Kingdom’s only land frontier with a member of the bloc.

That makes it one of the trickiest issues in the divorce negotiations—and the most sensitive, given Northern Ireland’s history of violence and conflicting identities in a region where some consider themselves British and others Irish. The fact that goods and people flow freely across the border has greatly helped reduce tensions since Northern Ireland’s 1998 Good Friday peace accord.

Especially for younger generations, it can be easy to forget the Troubles in Northern Ireland between 1968 and 1998, during which more than 3,500 died in a conflict between those loyal to the UK and those who wanted to separate from the UK and become part of Ireland to the south.

A writer for The Guardian remembered growing up near the border, where “random checkpoints on the country roads were a fact of life and army foot patrols a constant.”

“As the IRA bombing campaign escalated in the early 70s, the anarchy and excitement of the early Troubles gave way to an atmosphere that is hard to describe: a kind of prolonged and anxious enervation that could be fractured at any moment—by bombs going off in the town centre or the sound of gunfire in the night, in the Catholic housing estates.”

A writer for Smithsonian magazine described how residents of Belfast, Northern Ireland’s capital, were “sealed off in a patchwork of segregated neighborhoods divided by barbed wire and patrolled by masked guerrillas.”

Car bombs. Gunfights. Masked guerrillas. Constant anxiety. What sounds like a nation in the Middle East today was a reality for Northern Ireland during the Troubles.

In December 2017, Britain and the EU agreed that the all-but-invisible border would remain open once Britain leaves the bloc, although they left it unclear how that would happen in practice.

The EU’s chief Brexit negotiator Michel Barnier stated in the EU’s draft withdrawal agreement that there were three possibilities:

• A future free-trade agreement between Britain and the EU.

• “Specific solutions,” such as technological alternatives to a hard border, which the EU says it is still waiting for Britain to propose.

• A “backstop solution” of effectively keeping Northern Ireland inside the EU’s single market and customs union. The EU document proposes a “common regulatory area comprising the Union and the United Kingdom in respect of Northern Ireland.” It says that area would have no internal borders, and no customs duties or restrictions on imports and exports.

It is this last option that has inflamed the debate in Britain, with pro-Brexit politicians saying it would effectively impose a border between Northern Ireland and the rest of the UK, and prevent the UK from fully leaving the EU.

British Prime Minister Theresa May said the proposal would “undermine the constitutional integrity of the UK” and “no UK prime minister could ever agree to it.”

Mrs. May more recently proposed a border similar to that of the United States and Canada—an idea summarily dismissed by Irish Prime Minister Leo Varadkar.

“I visited the Canada/US border back in August and saw physical infrastructure with customs posts, people in uniforms with arms and dogs and that is definitely not a solution that we could possibly entertain,” he told reporters.

“Long Memory”

Those who lived through the Troubles reveal that the wounds from that conflict remain fresh—many of which have been reopened by Brexit.

Asked by The Guardian about the UK leaving the EU, Irish historian Roy Foster said: “The great Hubert Butler remarked in the 1950s that one could only hope that, with more pluralist attitudes north and south, the border would eventually become redundant and float away like a sticking-plaster from a wound that has healed. The combined effects of joint EU membership and the recognitions imposed by the Good Friday agreement were leading to something like that happening—a dilution of the border, culturally, economically and socially. All this has been destroyed by Brexit.”

Laurence McKeown, who took part in the infamous IRA hunger strike of 1981, also spoke with The Guardian.

He stated: “The old border had to do with conflict rather than customs and free movement. Now, it’s about the impact on cross-border businesses and the flow of people back and forth. And yet any form of a hard border would provide a viable context for dissident activity. If even one border checkpoint was to be attacked, all the rest would have to be fortified.”

The same Guardian article quoted George Knight, a 70-year-old Protestant historian who lives near the border. He recalled the Troubles: “Those were dire times along the border. We lived through the horror and we accepted it as normal.”

Asked whether he could see a hard border again, he responded: “At the moment, nothing would surprise me. There are so many possible consequences of Brexit and very few of them pertaining to Ireland were given a thought by the people who drove the decision to leave. We are separate nations with a huge common interest, but one thing that sets us [both] apart is that people here have such a long memory, because of what they lived through on this divided island, while people across the water seem to have no comprehension of that.”

Ireland and the United Kingdom do have a “huge common interest.” Yet the reason for the bond between Ireland and the UK—as well as why there is conflict between the nations—is deeper and more ancient than most realize.

For a fuller understanding of the bonds between Ireland and the UK, and what the future holds for these brother nations, read America and Britain in Prophecy.

This article contains information from The Associated Press.