President Bill Clinton, who helped broker the Good Friday Agreement, anticipated some of this. In a 1999 phone call with Prime Minister Tony Blair, Mr. Clinton tried to warn his British counterpart about the fate of the men of Northern Ireland. “You’re asking them to put a little white bread sandwich in a lunchbox and go off to work at the factory,” Mr. Clinton said. “It’ll be hard for them.” Mr. Blair responded that he had “put some people to work on” the issue.

But it doesn’t seem as if many people did “go to work” on healing Northern Ireland. Two-thirds of children in Creggan, a heavily Catholic housing estate on the edge of Derry, are born into poverty. Somewhere along the way it was forgotten that both veterans of the Troubles and their children might crave the status and purpose the conflict provided. The news crews and big-name politicians lost interest, and these neighborhoods were allowed to fester. The radicalization of young men is unsurprising.

The “peace process” was the term used to describe the series of talks and concessions between opposing sides that led to the first I.R.A. cease-fire in Northern Ireland in 1994. But since the Good Friday Agreement, the idea of “process” has been forgotten. The rest of Britain — and the world — seems to think of Northern Ireland as a place that is either at peace or at war. The fears that war could break out again are unfounded; it’s just that the peace has always been violent.

The reality is that Northern Ireland exists in a precarious post-conflict state. It is a place of both pain and of recovery. It cannot be abandoned by Britain or the rest of the world. The politicians of the United Kingdom and Northern Ireland must lead, and we all must pay more attention to these communities. The stakes are too high, as the killing of Ms. McKee shows. Wars take a long time to end, and peace is a process that must be protected.

Sinead O’Shea (@SineadEOShea) is the writer and director of the film “A Mother Brings Her Son to Be Shot.”

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