After hundreds of years of almost continuous warfare, 28 nations created the European Union. Now, the UK is becoming the first to go back on its own. The British exit, or "Brexit," began today, and nobody thinks the next two years are going to be pretty. Scotland might even declare independence from the UK. Remaining EU countries don't want to punish Britain, but they don't want to make leaving look easy, either. Can they agree on new rules for imports, exports, tariffs and immigration as six decades of cooperation ends in a historic divorce?