Europe is struggling to respond to the challenge posed by the thousands of jihadists who travelled to the battlefields of Syria or Iraq and have now begun to return home.
There was applause at the White House when President Trump announced he was pulling the US out of the Paris accord - but there were notable absences from the crowd.
On June 5, US officials joined world diplomats wading out into the Potomac estuary to replant seagrass in a telling gesture.
From waves of dinghies setting off from Libya to the appearance of privately-funded rescue ships, the face of the Mediterranean migration crisis has changed greatly over recent years.
Driven back by police batons and snarling dogs, or beaten and robbed by smugglers, migrants caught in Serbia have regularly been victims of violence.