Executive coach Ed Batista summarizes Warren Bennis and Robert Thomas’s Crucibles of Leadership:

A crucible is a vessel used in chemistry and metallurgy in which substances are transformed through the application of extreme heat and pressure. We can think of the current global crisis as a ‘crucible experience’—a chapter in our lives that will undoubtedly transform us, for better or for worse. In ‘Crucibles of Leadership’ Warren Bennis and his co-author Robert Thomas employ this metaphor as they explore the lives of leaders who went through such an experience, ‘a trial and a test, a point of deep self-reflection that forced them to question who they were and what mattered to them.’

Studying a number of leaders who overcame adversity in such circumstances allowed Bennis and Thomas to identify the four (five, really) characteristics identified above that these leaders shared.