When most Americans think of castles, they likely picture medieval fortresses towering over European hills. Yet the history of these imposing structures is much closer to home than many might realize.Speaking to Fox News Digital from England, historian Dan Jones described his latest book as a 3,000-year journey through human history, from the Sack of Troy to the Nuclear Age, as it explores the broader history of castles and fortifications.DIVERS UNCOVER ANCIENT TREASURES LINKED TO ROMAN GIANT WHO HELPED SHAPE AMERICAN HISTORYFrom Iron Age hillforts to classic medieval castles and beyond, "Castles: A Fortified History of the World," explores fortifications across different eras and regions of the world, including Japan's Himeji Castle and nuclear bunkers built during the Cold War.Jones examines the role America has played in the broader history of castles, from early fortifications to Civil War-era forts.Historian Dan Jones, pictured at left, explores 3,000 years of castles and fortifications in a new book, "Castles: A Fortified History of the World." (Fox News Digital; Thomas Koehler/Photothek via Getty Images)"I don't think we can truly understand it without having the American side to the story," said Jones.One notable example is Fort Sumter in South Carolina, where Confederate forces opened fire on Union troops in April 1861, marking the beginning of the Civil War.'HIGHLY UNUSUAL' CANNONBALL CACHE FOUND AT CONSTRUCTION SITE IN COASTAL CITY MAY BE WORLD'S FIRSTJones described Fort Sumter, a coastal fortress built with thick brick walls and artillery defenses, as one of the "descendants of castles" that emerged in America.Another important moment in the history of castle building, Jones said, came when Union forces attacked Fort Pulaski in Georgia with rifled cannons in 1862.Jones describes Fort Sumter as one of America's "descendants of castles," reflecting the evolution of defensive fortifications beyond medieval Europe.(VCG Wilson/Corbis via Getty Images; Fox ...