BEREHOVE, Ukraine -- Some 1,500 kilometers west of the front line in Russia's full-scale invasion of Ukraine, in a mountainous region that borders four EU countries, lies a red-roofed town whose several thousand ethnic Hungarian residents have acquired an outsized role in the standoff between Hungarian Prime Minister Viktor Orban and the European Union over whether Ukraine's membership talks should go forward. Berehove, just 7 kilometers from the Hungarian border, is the population hub for Ukraine's ethnic Hungarian minority of roughly 100,000 people. The street signs are written in both languages, Hungarian flags fly alongside Ukrainian and EU flags on...