Pictures: Five years of the European migrant crisis

Europe in 2015 suffered its worst refugee crisis since World War II, when over one million people fled to the continent. Above, refugees clamber through barbed wire as they cross from Serbia to Hungary, in Roszke, Aug. 27, 2015. Over 10,000 migrants, including many women with babies and small children, have crossed into Serbia and headed toward Hungary.

A paramilitary police officer investigates the scene before carrying the lifeless body of Aylan Kurdi who drowned in a failed attempt to sail to the Greek island of Kos.

Migrants are escorted through fields by police as they are walked from the village of Rigonce to Brezice refugee camp on October 23, 2015 in Rigonce,, Slovenia. Thousands of migrants marched across the border between Croatia into Slovenia as authorities intensify their efforts to attempt to cope with Europe's largest migration of people since World War II.

A German police officer and a migrant boy joking with the officer's cap while migrants wait for a bus after their arrival at the main train station in Munich, southern Germany in 2015. Faced with a record number of arrivals, European leaders vacillate and argue over how to deal with the situation. Fearing a humanitarian crisis, Germany's Chancellor Angela Merkel takes a stand, and her decision is a landmark moment. In August she announces Germany will no longer send asylum seekers back to their country of first entry into the EU, as rules require.

An estimated 30,000 migrants gathered at checkpoints near the Turkey Greece border. Migrants increasingly start arriving in Europe from 2011, the year the conflict in Syria began. But it is in 2015 that the situation takes on dizzying proportions.In April 2015 some 800 migrants from West Africa drown when a trawler sinks, in the worst disaster in the Mediterranean for decades. In late summer the number of arrivals rises and it tops a million over the year, with more than 850,000 going via Greece.

A helper putting a jacket on a refugee boy at the "Bayernkaserne", where clothes for migrants have been collected, in Munich, southern Germany. - It was five years ago that German Chancellor Angela Merkel made the controversial decision to open Germany's doors to tens of thousands of migrants, uttering the phrase that may yet come to define her time as chancellor: "We can do this!"

A young child cries as hundreds of migrants try to board a train at the Keleti Railway Station in Budapest, Hungary, Thursday, Sept. 3, 2015. Over 150,000 migrants have reached Hungary this year, most coming through the southern border with Serbia. Many apply for asylum but quickly try to leave for richer EU countries.

Migrants stand in line for food distributed by volunteers outside of derelict warehouses which they use as a makeshift shelter in Belgrade, as temperatures dropped to -15 degrees Celsius overnight in Sept, 2015.

Photo taken on September 06, 2015 migrants walk on platform after their arrival at the main railway station in Munich, southern Germany.

In this file photo taken on November 16, 2015, a family, along with other migrants and refugees, prepare to board a train heading to Serbia after crossing the Greek-Macedonian border near Gevgelija.

Refugees arrive on the shores of the Greek island of Lesbos after crossing the Aegean sea from Turkey on an inflatable boat on October 1, 2015 near village of Skala Sikaminias, Greece. Despite bad weather due to the upcoming Autumn, migrants and refugees are risking their lives in search of a better one in the European Union. Officals have warned that a rise in migrant deaths is expected as weather conditions gradually worsen.

Newly arrived migrants are kept behind a cordon as they wait to be let into a pre-registering site to allow them to be bussed to a newly opened asylum seeker's registration centre at the Office of Health and Social Affairs LAGESO in Berlin in 2015. Europe in 2015 suffered its worst refugee crisis since World War II, when over one million people fled to the continent.

Hundreds of refugees have already flocked to Turkey's border with Greece — or arrived in dinghies on the island of Lesbos

File photo taken on November 16, 2015, migrants and refugees walk after crossing the Greek-Macedonian border near Gevgelija.In total more than a million people reached Europe via the sea in 2015. Among them, more than 850,000 arrived on Greek shores, the majority Syrians fleeing their war-torn country.

Refugees and migrants are helped by volunteers as they arrive in Lesbos in Greece.