Migrants wait to cross the Slovenia-Austria border in Sentilj, Slovenia, October 27, 2015. The first five border guards – all German – of 400 promised to Slovenia by fellow EU countries are expected to arrive on Wednesday to help channel a huge flow of migrants through the tiny Alpine state, its government said. Interior Ministry state secretary Bostjan Sefic also said 100-120 customs police would join Slovenian soldiers, regular police and private security firms in dealing with an influx that has strapped the country's limited resources. (Photo by Srdjan Zivulovic/Reuters)

The waning moon is setting over the mountain “Les Cornettes de Bise” located at the border of the Haute-Savoie and the Valais canton of Switzerland in the Chablais Alps, photographed from Glutieres, January 7, 2015. (Photo by Anthony Anex/EPA)

Photographers help a Rohingya refugee to climb out of Naf River as they cross the Myanmar-Bangladesh border in Palong Khali, near Cox's Bazar, Bangladesh on November 1, 2017. (Photo by Hannah McKay/Reuters)

A Syrian boy looks through a gate as others wait to cross into Syria at Oncupinar border crossing in the southeastern city of Kilis, Turkey February 11, 2016.. (Photo by Osman Orsal/Reuters)

A migrant tries to restrain her tent from strong winds in a makeshift camp for refugees and migrants at the Greek-Macedonian border near the village of Idomeni, Greece, March 24, 2016. (Photo by Alexandros Avramidis/Reuters)

A Palestinian protester uses a sling shot to throw stones towards Israeli security forces during clashes on the Israeli border Eastern Gaza City, Friday, November 6, 2015. (Photo by Adel Hana/AP Photo)

People stand by a damaged car at a train station at a makeshift camp for migrants and refugees at the Greek-Macedonian border near the village of Idomeni, Greece, May 10, 2016. (Photo by Marko Djurica/Reuters)

Border between Sweden and Norway at Moldusen. An approximately 20-meter wide clearing in the forest separates the two Scandinavian nations, consequently cutting Finnskogen in two. Grue Finnskog 2016. (Photo by Terje Abusdal/The Washington Post)