A REMINDER FOR MEMORIAL DAY, from Frederick Kempe’s Berlin, 1961. “I want Americans to understand how the decisions of their presidents — then and now — shape world history in ways we don’t always understand at the time of a specific event. I want readers to know that Kennedy could have prevented the Berlin Wall, if he had wished, and that in acquiescing to the border closure he not only created a more dangerous situation — but also contributed to mortgaging the future for tens of millions of Central and Eastern Europeans. The relatively small decisions that U.S. presidents make have huge, often global, consequences.”