In 1952, Bullock published "Hitler: A Study in Tyranny", the first comprehensive biography of Adolf Hitler, which he based on the transcripts of the Nuremberg Trials. This book dominated Hitler scholarship for many years. The book characterised Hitler as an opportunistic "Machtpolitiker" ("power politician"). In Bullock's opinion, Hitler was a "mountebank", an opportunistic adventurer devoid of principles, beliefs or scruples whose actions throughout his career were motivated only by a lust for power. Bullock's views led in the 1950s to a debate with Hugh Trevor-Roper who argued that Hitler did possess beliefs, albeit repulsive ones, and that his actions were motivated by them. Bullock's "Guardian" obituary commented that "Bullock's famous maxim 'Hitler was jobbed into power by backstairs intrigue' has stood the test of time."