There is a difference, of course, between a true leader and a person who's simply in charge -- but what, precisely, is that difference? On this edition of ST, our guest is Nancy Koehn, an historian who teaches at the Harvard Business School, where she holds the James E. Robison Chair of Business Administration. She joins us to discuss her new book, "Forged in Crisis: The Power of Courageous Leadership in Turbulent Times." This volume studies the lives and works of five renowned leaders: polar explorer Ernest Shackleton; President Abraham Lincoln; legendary abolitionist Frederick Douglass; Nazi-resisting clergyman Dietrich Bonhoeffer; and environmental crusader and writer Rachel Carson. As was noted of this book in a starred review in Kirkus: "[An] engaging, unusually rewarding book.... Throughout, Koehn underscores the great humanity and depth of understanding of these leaders.... Wise, thoughtful, and valuable, this book will foster a new appreciation for effective leadership and prompt many readers to lament the lack of it in the world today."