(CNN)Five of CNN's correspondents gathered recently to discuss how the world changed in 2015 and what may come in the year ahead. Nick Paton Walsh, Nima Elbagir, Ivan Watson, Clarissa Ward and Arwa Damon sat down with videographer Claudia Morales and talked about the stories, issues and people they had covered. See their conversations in a series of videos and catch up on the key stories of our time. Here, the refugee crisis. Also in the series: ISIS; Russia
Refugee crisis: What happened in 2015 and what's ahead
The boats just kept coming and coming. Wave after wave of people fleeing war, persecution or hardship trying to reach safety and the promise of a better life in Europe.
While migration to Europe is nothing new, this year saw an unprecedented surge of arrivals, creating humanitarian, logistical and political crises.
The rise of ISIS, the Syrian civil war, and instability in Afghanistan, the Middle East and elsewhere drove record numbers of people to leave their homes and try to make the crossing to Europe. On December 22, that number topped one million people, according to the International Organization of Migration.
In April, tragedy followed tragedy with shipwrecks and sinkings killing people who'd boarded rickety boats in Libya heading for Europe.
"A mass grave is being created in the Mediterranean Sea and European policies are responsible," Loris De Filippi, the president of the international aid group Doctors Without Borders, said at the time.
European nations stepped up rescue missions and the daily death toll dropped, but did not vanish. Some 3,692 deaths of migrants were recorded by mid-December.
And still the people came, across the western Mediterranean and increasingly over the eastern Mediterranean, leaving from Turkish beaches, and overland.
Those who reached Greece were in the European Union, but their journeys often didn't end there. They tried to get further north, perhaps to Germany, where opportunities and welcome are seen as greater. And those journeys again brought tragedy -- in one case, 71 abandoned to die in a truck in Austria -- and confusion, with borders restrictions increased and relaxed in different countries.
But still the people came. And still death followed.
In September, a photographer captured an image of a Syrian toddler washed ashore on a Turkish beach. The death of Aylan Kurdi provoked international anguish, prompting some governments to open their doors a little further while others kept them firmly closed.
The exodus from Greece, through Macedonia, then Serbia to Hungary, Austria and Germany saw some refugees helped, others treated like animals.
And still the people came.
There's no indication the flood of humanity will stop, not with the situations in Syria, Afghanistan and Iraq still so awful, as well as the many refugees and migrants from Africa.
Even if solutions emerge in the migrants' home countries, European leaders must still deal with the hundreds of thousands of people already seeking refuge in Europe -- and the many more in camps in Turkey, Jordan and elsewhere.
In the United States, how to handle Syrian refugees in particular became an issue in the 2016 presidential campaign amid fears of a terror threat, bringing national security to the fore.