Catholic leaders fear a revival of border tensions in Ireland following Brexit. As the United Kingdom prepares for its withdrawal from the European Union, Catholics in parishes and dioceses split by the border are concerned that any return to a "hard border" could mean real effects on their day-to-day lives.

Archbishop Eamon Martin of Armagh, the Primate of All-Ireland, has spoken of his own concerns and said he remembers the days of a hard border. Speaking to the Irish Catholic newspaper Sept. 27, he discussed how the reality of the physical divide shaped the community.

Martin grew up near two of Derry's major border checkpoints. These were "heavily fortified" and themselves became "symbols of division and therefore attracted violence, attacks, and indeed death and destruction," he recounted.

The border was one of the concerns he discussed during his September trip to Poland for the Council of the Bishops' Conferences of Europe, held Sept. 13-16 in Poznan. The council includes bishops from 39 European bishops' conferences.

"I therefore expressed the nervousness of the communities that live on the border that any return to border structures and barriers could attract violence and could become sparks or tinderboxes for strife once more," said Martin.

The Archdiocese of Armagh, which traces its origins back to the ministry of St. Patrick in the fifth century, is divided by the border, with 40 percent of its Catholics in the Republic of Ireland and 60 percent in Northern Ireland.

Martin said other European bishops were intrigued by a diocese and its parishes divided by a political border, which is "quite unusual" in Europe.

Several of the bishops there voiced concerns about Brexit, set to take effect March 29, 2019, the final terms of which are still unclear.

The 310-mile border between the Republic of Ireland and British province of Northern Ireland will be the only land border between the UK and the EU. With both countries currently under the EU's shared legal framework, the once fiercely contested border has been effectively invisible for decades.

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In June 2016, UK citizens voted to leave the European Union by 52 to 48 percent. More locally, 56 percent of Northern Ireland's voters wanted to remain. While the terms of the UK's departure remain under negotiation, concerns have been raised that a British exit from the EU's free-trade area and customs union could require a return to some formal barrier between the two jurisdictions along the Irish border.

Archbishop Martin said he had discussed with Europe's bishops how the European movement was crucial to the peace process in Ireland, telling the Irish Catholic newspaper that "the solidarity of other European countries formed a very important backdrop and canvas upon which the Irish peace process was written."

He praised the work of Northern Ireland politician John Hume, who won the Nobel Peace Prize for his work on peace in Ireland.

In Martin's words, Hume "effectively used the European platform to bring us beyond the kind of squabbles and narrow understanding of nationalism which could itself engender strife and division."

"Hume was very much somebody who spoke about our common belonging to Europe as something that lifted us beyond the interior strifes and struggles that could happen between near neighbors. In other words, he was about bridges rather than borders," the archbishop said.

The border dates back to a partition agreement in 1921, leaving Northern Ireland predominantly with pro-union Protestants. The Republic of Ireland gained full independence in 1948. The following decades saw Irish Republican Army bombing campaigns along the border. This was followed by violence between republican and unionist paramilitaries within Northern Ireland itself, further complicated by British military intervention, from the late 1960s through the Good Friday Agreement signed in 1998.

The period of violence, collectively known as "the Troubles," killed 3,500 people, mostly non-combatants, Bloomberg News says.

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The tensions, largely divided along Catholic-Protestant lines, resulted in many physical barriers. In the Northern Irish capital of Belfast, tall barricades still separate some Catholic and Protestant neighborhoods.

But following recent decades of stability, many young people have no memory of a physical border.

Some families have members on both sides of the border. Workers, businessmen, university students, shoppers and other visitors could face increased difficulties traveling to businesses or schools. Medical patients could be cut off from the closest hospitals.

Farmers and fishermen also face their own difficulties.

In the County Armagh border village of Jonesborough, one village church is in Northern Ireland, and its graveyard is in the Republic of Ireland.

Jonesborough area resident and farmer Damian McGenity told Public Radio International of his own fears.

"My wife works in the south, we get fuel and food in the south, I buy farm supplies in the south," he said. "Socially, if you go out to a restaurant, or see a football game, you would typically go to Dundalk in the south. All of that would be disrupted."

During the Troubles, the customs post at the nearby village Killeen was the site of many bombings and shootings.

"Nobody wants to go back to any kind violence or trouble," McGenity said. "Absolutely not. But when you create the situation or the possibility of it, you take the lid off the Pandora's Box. It's madness, when there is complete peace here."

EU leaders have been negotiating in Salzburg and an EU leaders' summit is set for Brussels later this month. Oct. 17-18, Reuters reports. EU officials and diplomats hope for an agreement on a final withdrawal treaty offer, with further declarations on a future UK-EU trading relationship.

The situation is further complicated by the presence of the Democratic Unionist Party, the largest party in Northern Ireland, in the governing coalition of British Prime Minister Theresa May.

Mrs. May has agreed with Republic of Ireland leaders on the need for a "backstop" to ensure the border remains completely open to trade, people and services if no agreement is reached in time for formal UK withdrawal. At the same time, she has agreed to meet DUP concerns about maintaining its regulatory unity with the rest of the UK and preventing the creation of a border between Northern Ireland and the rest of the kingdom, which the DUP fears could further loosen political unity between the province and the rest of the country.

The EU is backing a "common regulatory area" between Ireland and the UK in Northern Ireland to protect its regulatory standards and its shared single-market between EU members. The UK Parliament remains divided between those seeking a "Brexit of least resistance" which would minimize economic and regulatory disruption, and those favoring a so-called "hard" or "clean" Brexit which, it is argued, could boost the UK's freedom to broker free-trade agreements with other countries.