In the most basic sense, Fritz Fischer, with his 1961 publication of Griff nach der Weltmacht (roughly translated as Germany's Aims in the World War I), painted a most unflattering picture of Imperial Germany. The controversial Fischer Thesis blamed Germany for the causes of World War I in 1914, focusing on Bethmann-Hollweg's September Program and its imperialist aims, and asserting that it was Germany's bid for world power that brought on the conflict. By the time Fischer had published his thesis, Europeans, in the aftermath of the Second World War, had largely agreed that blame for the First should be equally distributed among all participating nations - "We all stumbled into it," as Lloyd George had said.
The Fischer Thesis and WWI
The Fischer Thesis reawakened the controversy surrounding the outbreak of World War I and argued that in July of 1914 Germany took advantage of the Sarajevo incident to begin a "defensive" European campaign. This, in contrast to the traditional German stance, which continued to maintain that Germany's entry into the war was accidental and nothing if not defensive, coming on the heels of an unanticipated Russian mobilization; also, the ensuing invasion of France was made because of Germany's fear of being encircled by the other European powers, and as a result of the Schlieffen Plan.
Fischer uncovered German and Prussian archival documents that clearly demonstrated Germany's intent to establish a "Greater Germany" as early as 1897 as part of their Weltpolitik strategy. Such a "Greater Germany" as was described there could only have been accomplished by going to war against both France and Russia. The German nationalist sentiment continued to grow through 1912, when William II's War Council advised the German government to prepare for war and won approval from Bethmann-Hollweg. Sarajevo was but a convenient excuse for the pan-European war imperialist Germany had been planning for several years.
The Controversial Fischer Thesis
The Fischer Thesis has been especially controversial because it seeks to establish a continuity between pre-World War I Germany and the Third Reich - refuting the German school of apologists who had labored to disassociate the 12-year long Nazi regime from the rest of German history (interestingly, Fischer accomplished this while not mentioning Nazism even once).