Refugees plead for family members to be allowed on to buses on September 18, 2015 in Tovarnik, Croatia. The migrants had just walked across the border from Serbia and were camped on a residential street awaiting transportation. Police regulated the flow of people by creating a cordon around the vehicles, but they could not confirm the final destination of the buses.
Migrants walk through fields, circumventing official checkpoints, from the Serbian to the Croatian border on September 17, 2015.
Five year-old Ali, from Baghdad, chants "Open Border!" with frustrated migrants who have been waiting for hours to cross into Slovenia on September 19, 2015 in Harmica, Croatia.
Migrants walk through cornfields west of Sid, Serbia towards the Croatian town of Tovarnik on September 17, 2015. After being bussed to the border, migrants were directed by aid workers and police on a route that circumvented the official checkpoints of both nations.
Aid workers distribute food to migrants at the Austrian border on September 20, 2015 near Hegyeshalom, Hungary. After walking from the nearby town's train station migrants waited for hours in a transit zone parking lot. Thousands of people waited in line to catch buses and taxis to Nickelsdorf, Austria where they would board trains bound for Vienna.
Syrian migrants, who are hoping to reach London, share cigarettes at Wien Hauptbahnhof train station on September 22, 2015 in Vienna, Austria.
Flyers on a wall, written in Arabic, German and English, seek information on missing persons at the east entrance of Wien Hauptbahnhof train station on September 22, 2015 in Vienna, Austria. While the west side of the station features long lines as migrants wait to purchase tickets to Germany and other locations in Europe, the east entrance of the station has been converted into a refugee center, featuring a kitchen, a childcare center, legal aid and a clothes distribution area.
Migrants sit in the road at the closed Hungrian border on September 17, 2015 in Horgos, Serbia.
A young girl cries as Slovenian police prevent migrants from crossing the border on September 19, 2015 in Harmica, Croatia.
Migrants bathe at a spigot next to the Hungarian border fence on September 17, 2015 in Horgos, Serbia. Thousands of migrants were left in limbo after Hungarian police sealed the border with a barbed wire fence and used tear gas to push back crowds.
Migrants pass a young child across the border to Slovenia on September 19, 2015 in Harmica, Croatia.
Razor wire and barriers block a border crossing on September 17, 2015 between Horgos, Serbia and Röszke, Hungary.
Migrants converse while using a generator to charge their phones on September 17, 2015 in Horgos, Serbia.
A migrant's foot, clad only in sandals, is seen as he waits to board a train near the Croatian border on September 25, 2015 in Zakany, Hungary.
A woman asks a police officer to let her and her family through the Slovenian border on September 19, 2015 in Harmica, Croatia.
Migrants pack up their tent as brush adjacent to the border fence burns in the background on September 17th, 2015 in Horgos, Serbia. Police questioned nearby refugees about who started the fire, simultaneously, migrants blamed police for starting the fire to make it easier to monitor the border.
A partially defaced "Refugees Welcome" poster is seen on September 22, 2015 in Vienna, Austria.
A migrant peers through a train window covered with condensation after crossing the Croatian border on September 25, 2015 in Zakany, Hungary.
A field houses a tent city in between two closed border crossings on September 17, 2015 in Horgos, Serbia.
Hungarian soldiers construct a razorwire fence on the Croatian border on September 25, 2015 in Zakany, Hungary.
Members of Hungarian law enforcement walk past a train filled with migrants near the Croatian border on September 25, 2015 in Zakany, Hungary.
A migrant peers through the now-closed Hungarian border on the highway on September 17, 2015 in Horgos, Serbia.
Migrants push against police in riot gear at the Slovenian border on September 19, 2015 in Harmonica, Croatia.
An Austrian police officer counts migrants as they enter Austria on September 20, 2015 near Hegyeshalom, Hungary.
Frustrated migrants implore authorities to open the border to Slovenia on September 19, 2015 in Harmica, Croatia. After Hungary sealed its Serbian border, many migrants sought a new route to Western Europe through Croatia. In Harmica, Slovenian police installed barriers and formed a skirmish line, intermittenly allowing migrants to cross into Rigonce.
An Iraqi child, suffering from a neurological disorder, waits with his family for buses heading to Zagreb and points west on September 18, 2015 in Tovarnik, Croatia.
Migrants from several countries sing and dance as Austrian artist Walter Steinacher plays a drum near where they are camped at Vienna's Hauptbahnhof train station on September 21, 2015 in Vienna, Austria.
Thousands of people wait in line to catch buses and taxis to Nickelsdorf, Austria where they will board trains bound for Vienna on September 20, 2015 near Hegyeshalom, Hungary. After walking from the nearby town's train station migrants waited for hours in this transit zone parking lot.
All images copyright Pete Kiehart or The San Francisco Chronicle unless otherwise noted. Don't steal photos.