The Northern Ireland "Troubles" - really a low-grade civil war - lasted 30 years. During that period, more than 3,600 people died from car bombs, street violence or skirmishes between Catholic paramilitaries who wanted to join the Irish Republic and Protestant Unionist paramilitaries who wanted to stay in the United Kingdom.
The problem seemed intractable precisely because it was so black and white. Catholic vs. Protestant, united Ireland vs. United Kingdom: There seemed no room for compromise. But when the Good Friday agreement was negotiated in 1998, a compromise was found. Devolution of power from London to Belfast helped. But so did the European Union.
Because both Ireland and Britain were EU members, no border was needed between the two. Because the EU had harmonized regulation, trade was smooth. Residents of Belfast who wanted to be Irish could get Irish passports. Thousands did - including Protestants. The question of which group would rule didn't disappear so much as dissolve. Things grew blurrier. Sovereignty, once everyone agreed to share it, ceased to be a source of conflict.
The struggle for influence didn't exactly go away. But the violence morphed into something else: a bureaucratic tangle, an unending argument, a squabble about power- sharing. Over time, the whole Northern Ireland problem became . . . boring.
Boring was a lot better than violent. But it also meant that Northern Irish politics drifted off London's front pages, migrating into history books and West End plays. During the Brexit referendum campaign, it barely figured. Immediately afterward, I happened to be in Belfast. "They forgot about us," someone told me.
This week, they were forced to remember, because Britain's decision to leave the EU - which was partly motivated by people who want a return to old-fashioned forms of sovereignty - has the potential to drag Northern Ireland out of the realm of blurred identities and back into the clear blue, zero-sum, black-and-white world of stark choices.
The most important one sounds like a technicality: If Britain leaves not only the European Union's political institutions (which is certain) but also its customs union (which is optional, though the Brexiteers are pushing for this), then there has to be a customs border between Britain and Ireland.
Either that border can run through the middle of the island, once again separating north and south, or it can lie, in effect, in the Irish Sea, between the island of Ireland and the British mainland.
The construction of a border through the island is not just unpopular; it is probably also impossible. There are hundreds of roads and paths across the border, not to mention fields and forests that straddle it. Chances that border posts would be circumvented, ignored, vandalized or worse are high; the possibility that the border would revive the Irish Republican Army cannot be excluded. British Prime Minister Theresa May took the other road: Perhaps Northern Ireland and the Republic could maintain "regulatory alignment" - a curious phrase that could imply that the North stays in the customs union with Ireland, while the rest of the U.K. takes off in a different direction. In other words, the border would move to the Irish Sea.
The result? May's coalition partners, the Democratic Unionists, revolted. Suddenly, they feared losing sovereignty once again. Their leader could not have been more clear: "We will not accept any form of regulatory divergence which separates Northern Ireland economically or politically from the rest of the United Kingdom." Negotiations ground to a halt.
The solution, announced with great fanfare early Friday, was - and yes, this is the technical term used by the experts - a "fudge." It was an agreement to agree later, to talk about it in a couple of years when the other elements of the EU/U.K. relationship are clearer. It is still possible that Northern Ireland will wind up with special status. It is still possible that the British government, under this prime minister or another one, will wind up inside the customs union.
The squabble was suppressed beneath the bureaucratic EU language everyone loves to hate. But it offered a brief hint of the conflicts that could be brought to life when the smothering blanket of European law is removed from Britain. It was also a reminder of what united Europe, with its boring consensus procedures, achieved even in Britain, a country that never fully accepted this way of doing things.
Certainly there are drawbacks to shared sovereignty of the kind the EU requires. In Northern Ireland, both sides had to give things up. Neither is entirely satisfied.
The political squabble for power - not only along the Irish border but along the Franco-German border, the Hungarian-Romanian border and many others, too - is dull and unsatisfying. But no one dies.