Many people regard the signing of the Good Friday Agreement on April 10 1998 as signalling the end of the Troubles. The United States played an enormously positive role in the negotiations that forged the deal, and it is highly unlikely that power-sharing and devolution would ever have become a reality without the commitment of Senator George Mitchell and President Bill Clinton.
It is therefore deeply depressing that the Agreement's 25th anniversary and the final preparations for the visit of the current incumbent of the White House, President Joe Biden, took place against the backdrop of violent attacks against the PSNI in Derry.
An especially alarming feature of the disturbances, which took place during an illegal anti-agreement dissident republican parade in the Creggan area, was the youth of many of those involved in hurling petrol bombs at a police Land Rover.
As well as teenagers, children - some of whom appeared to be of primary school age - were in the forefront of the attack, which had all the hallmarks of being orchestrated by adults and, with a large supply of petrol bombs, of being premeditated.
It is fortunate that no serious injuries - to either police officers or their young attackers - have been reported, though this must be more by luck than judgment, given the reckless nature of the violence.
The image of children attacking the PSNI a quarter of a century after the Agreement should haunt all of us. It emphasises not only the fragility of our peace, but also the failure in our politics.
Everyone who hoped that such scenes would be firmly in the past will agree with Chief Superintendent Nigel Goddard who described the episode as "disheartening".
As political leaders across the spectrum condemned the attack, Sinn Féin vice-president Michelle O'Neill said, correctly, that this sort of street disorder "has no place in our society".
Another sinister development which must be condemned in the strongest terms is the New IRA's claim that it continues to "recruit, train and target" just weeks after it attempted to murder Detective Chief Inspector John Caldwell.
He was shot while putting footballs into his car after a youth coaching session - circumstances which, police said at the time, "could also quite easily have killed or seriously injured children".
That potentially deadly disregard for young lives is a chilling feature of both February's shooting of Mr Caldwell and this week's trouble in Derry. Those who cling to the dead hand of militant dissident republicanism can offer no justification for dragging children into their sordid struggle.