Europe’s Refugee Crisis A volunteer helps Middle Eastern refugees ashore at the Greek island of Lesbos on November 29, 2015. Exhausted and emotional, they traveled by boat from Turkey. Under Europe’s system of open internal borders, the island’s thinly patrolled, easily accessible coastline, within sight of the Turkish coast, offered a tempting entry into the European Union for migrants ultimately seeking residence in Germany or Sweden. In fall and early winter of 2015–2016, about five thousand refugees reached Europe each day along the so-called Balkan migrant route. Their unprecedented numbers stoked anti-immigrant tensions across Europe and called into question the internal open-border system.

(Oage Elif Kizil/Anadolu Agency/Getty Images)