Book excerpt: George R.R. Martin's A Song of Ice and Fire novels and HBO's Game of Thrones series depict a medieval world at war. But how accurate are they? The author, an historian and medieval martial arts expert, examines in detail how authentically Martin's fictional world reflects the arms and armor, fighting techniques and siege warfare of the Middle Ages. Along the way, he explores the concept of "medievalism"--modern pop culture's idea of the Middle Ages.