Hugo Jaeger captures Austrian crowds, ecstatic at the notion of Austria and Germany uniting under one government, as they cheer Hitler's 1938 campaign to unite the two German-speaking nations. Here, and in several other galleries on LIFE.com, are rare and never-before-published photographs from Jaeger's astonishing collection -- along with the equally amazing story of how Jaeger buried the photographs (literally buried them, in the ground) for years before bringing them to light.