Thomas B. Allen is the author of many books on subjects ranging from military history to espionage to sharks. He has written several acclaimed titles for National Geographic, including Remember Pearl Harbor; George Washington, Spymaster; and Harriet Tubman, Secret Agent. Allen lives in Bethesda, Maryland, where he is a founding member of the Writer's Center. To learn more, visit tballen.com. ROBERT D. BALLARD is among the most accomplished and well known of the world's deep-sea explorers. He is renowned for his historic discoveries of hydrothermal vents, the sunken RMSTitanic, the German battleshipBismarck, and numerous other contemporary and ancient shipwrecks around the world. During his long career he has conducted more than 120 deep-sea expeditions using the latest in exploration technology, and he is a pioneer in the early use of deep-diving submarines. In 2003, President George W. Bush presented him with the National Humanities Medal in the Oval Office of the White House.