Two decades of frontier-free travel across Europe unraveled Monday as countries re-established border controls in the face of an unprecedented influx of migrants.
Germany's surprise decision to restore border controls on Sunday had a swift domino effect, prompting neighbors to impose checks at their own frontiers as thousands of refugees pressed north and west across the continent.
The inrush broke the record for the most arrivals by land in a single day, and Hungary sealed the main informal border crossing point into the European Union.