Peter Duffy, author of the 2003 book “The Bielski Brothers,” lamented the lack of a unified collection of these testimonies in a conversation with me recently. “There’s this sense that we’ve done enough on this history. People say, ‘Oh, another Holocaust book, or another memorial,’” he told me. But Mr. Duffy believes that when it comes to what transpired in these forests, “we’ve barely scratched the surface of the story that is there, and probably most of it is lost.” The history is so elusive, in fact, that scholars at The Polish Center for Holocaust Research have called these less-understood stories of Jews who escaped their ghettos and attempted to hide “the margins of the Holocaust.”