The boundary between the Republic of Ireland and Northern Ireland was long the scene of tense checkpoints and violent protest. Nearly two decades after the end of a conflict that claimed 3,500 lives, the undulating border is once again caught up in a bitter division. When British and European Union leaders carry out the split -- Brexit -- that British voters ordered up, the border between Ireland’s north and south will be the only land crossing between the two jurisdictions. For now the border is effectively open, meaning people and goods are free to cross back and forth. Whether it remains that way is the most vexing issue in the divorce talks.

1. Could Brexit mean a return of border checks?

That’s one scenario -- a return of customs controls, along with the delays and costs that would entail. But since cross-border trade is worth more than 3 billion euros ($3.5 billion) a year, there’s a desire to avoid disruptions, especially given concerns that a return to checkpoints and watchtowers could endanger the region’s peace process. Both sides broadly agree that people and goods should move seamlessly back and forth. There’s a discussion about possible technical solutions, such as cameras, drones and a system for pre-clearing goods. So far though, there is no sign of an agreement.

2. Why is there a border in the first place?

The island was partitioned in 1921 as part of a peace agreement between the U.K. government and Irish rebels seeking independence. As part of the deal, Northern Ireland, where the population is majority Protestant, remained part of the U.K. with England, Scotland and Wales. The mostly Catholic southern part of the island became the Irish Free State and gained full independence in 1948. Today the border runs north-south in some places, east-west in others, meandering through countryside for some 310 miles (500 kilometers), dividing rivers, fields and even some houses. A change in road signs and accepted currency is pretty much the only indication that a person has moved into a different jurisdiction.

3. Where do negotiations stand?

Up in the air. While an initial agreement on the border was painstakingly reached in December, the issue erupted again after the EU published a draft withdrawal agreement on Feb. 28. That text laid out a proposal for a so-called backstop -- an assurance that, whether or not a final Brexit agreement is reached, Northern Ireland would effectively remain aligned with the EU’s Customs Union and single market. That idea was rejected out of hand by U.K. Prime Minister Theresa May, who sees it as threat to her nation’s territorial integrity. The EU has since softened its stance, raising the possibility that customs checks could be conducted away from the border, perhaps on the premises of companies. The U.K. rejected that too, with little movement expected before the Conservative Party annual conference ending Oct. 3.

4. What is the U.K.’s proposal?

May proposes a blueprint for a new U.K.-EU “free trade area,” with interwoven customs regimes and identical regulations for industrial and agri-food goods. That plan -- hammered out at her Chequers country retreat in July -- could avoid a hard border, but it faces stiff opposition. Within her own party, Brexit advocates view it as a ruse to stop a clean break with the EU, essentially keeping the U.K. in the bloc by stealth. The EU rejects May’s idea as cherry-picking the best bits of the single market.

5. Who else is weighing in?

The Democratic Unionist Party, Northern Ireland’s biggest political party and an essential part of May’s governing majority, is adamant that Northern Ireland will leave the EU on the same terms as the rest of Britain. The party says it won’t accept any deal that separates the territory economically or politically from the rest of the U.K. On the EU side, French farmers have objected to an open Irish border out of concern that cheaper non-EU imports will infiltrate the bloc via the U.K.

6. How does the open border work now?

Businesses are able to work across the entire island. Diageo Plc, the maker of Guinness and other beverages, has brewing operations on both sides of the border and sends its trucks across about 18,000 times a year. Similarly, the free movement of horses has helped make Ireland a world leader in the bloodstock industry, which includes racing and breeding, adding about 1 billion euros to the economy. As for humans, an estimated 30,000 people pass through 300 different crossings every day.

7. What does this fight mean to Ireland?

At the very least, it brings back bad memories. The border has been a symbol of British rule almost since it was created, with customs and later military checkpoints positioned at crossings over the course of decades. The Irish Republican Army, which wants a united Ireland, waged a bombing campaign along the border in the 1950s and 1960s. Violence between republican and unionist paramilitary groups claimed about 3,500 lives from the 1970s onward before the arrival of the European single market and a peace accord in the 1990s, when border controls largely melted away.

8. Could a hard border lead to the return of violence?

Customs and security checks would likely hurt the economy on both sides of the border, and perhaps offer a daily reminder of British rule of Northern Ireland. While the province has been at peace for almost two decades, Martin McGuinness, Northern Ireland’s former deputy leader, warned a year before his death in 2017 that the reintroduction of a border following Brexit could aid those who oppose the region’s peace process. Other politicians argue that peace is now so deeply rooted that it would take more than a few border posts to disrupt the island.

To contact the reporter on this story: Peter Flanagan in Dublin at

To contact the editors responsible for this story: Dara Doyle at, Leah Harrison Singer

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