During World War II, most of Europe's last monarchies collapsed. Under Tsar Boris III, Bulgaria had been a reluctant ally of Hitler's Germany, refusing to send troops to fight the Soviets and resisting the Holocaust. But after Boris died in 1943, the Red Army entered the country, and communists executed much of the royal family and sent the boy-tsar, Simeon II, into exile, first to Turkey and Egypt, then to Spain. In 2001, Simeon was elected prime...