Sir Ian Kershaw, FBA (born 29 April 1943) is an English historian and author whose work has chiefly focused on the social history of 20th-century Germany. He is regarded by many as one of the world's leading experts on Adolf Hitler and Nazi Germany, and is particularly noted for his biographies of Hitler.He was the leading disciple of the late German historian Martin Broszat, and (until his retirement) professor at the University of Sheffield. Kershaw has called Broszat an "inspirational mentor" who did much to shape his understanding of National Socialist Germany. Kershaw served as historical adviser on numerous BBC documentaries, notably The Nazis: A Warning from History and War of the Century. He taught a module titled 'Germans against Hitler'.