Young people in Northern Ireland will be "groomed into violent activity" if a hard border emerges after Brexit, a new report has warned.
The return of violence is inevitable with the "only issue" being on what scale, it said.
The study compiled by the chairs of two Unesco committees also warns that rushing into a referendum on a united Ireland would also result in conflict.
A key problem identified by Professors Mark Brennan and Pat Dolan is that the 'Agreement generation' has no memory of the harm caused by the decades of bloodshed.
They say older people have not shared enough about "the horrors of war" that is termed "the period of the Troubles".
Instead some of the violence has been "romaniticised".
"This lack of capacity to discuss in real ways what happened can unintentionally act in favour of those who would prefer to give youth (and particularly vulnerable and impressionable young people) a false, almost romantic, retrospection of the past up to and including a very sectarian analysis," the report said.
It adds that nationalist youths who are marginalised will be susceptible "to being groomed into violent activity by dissident republicans including the 'New IRA'", which detonated a car bomb outside the courthouse in Londonderry last month.
The professors say the deconstruction of a border "swiftly after its creation could become the absolute raison d'etre for youth becoming engaged in violence".
The report added: "In as little as six weeks it is possible that a hard border could materialise due to a no-deal Brexit triggering a return to violence in Northern Ireland."
It said "all indications" that pushing for a border poll against this backdrop - as advocated by Sinn Fein - would also spark violence.
"The only question in both scenarios will be the scale of the violence."
Professor Brennan is the Unesco chair for community, leadership and youth development and professor of leadership and community development at the Pennsylvania State University.
Professor Dolan is director of the Unesco child and family research centre at the National University of Ireland, Galway and holds the Unesco chair in children, youth and civic engagement.
They were assisted by Michael Ortiz, a counter-terrorism expert and former security adviser to the Obama administration.