of the two schools, though leaning towards the functionalist school. Despite some disagreements, Kershaw has called Mommsen a "good personal friend" and an "important further vital stimulus to my own work on Nazism". Kershaw has argued in his two-volume biography of Hitler that Hitler did play a decisive role in the development of policies of genocide, but also argued that many of the measures that led to the Holocaust were undertaken by many lower-ranking officials without direct orders from Hitler in the expectation that such steps would win them favour. Though Kershaw does not deny the radical antisemitism of the Nazis, he favours Mommsen's view of the Holocaust being caused by the "cumulative radicalization" of Nazi Germany caused by the endless bureaucratic power struggles and a turn towards increasingly radical antisemitism within the Nazi elite. Despite his background in the functionalist historiography, Kershaw admits that his account of Hitler in World War II owes much to intentionalist historians like Gerhard Weinberg, Hugh Trevor-Roper, Lucy Dawidowicz and Eberhard Jäckel. Kershaw accepts the picture of Hitler drawn by intentionalist historians as a fanatical ideologue who was obsessed with social Darwinism, völkisch antisemitism (in which the Jewish people were viewed as a "race" biologically different from the rest of humanity rather than a religion), militarism and the perceived need for Lebensraum. However, in a 1992 essay, "Improvised genocide?", in which Kershaw traces how the ethnic cleansing campaign of Gauleiter Arthur Greiser in the Warthegau region annexed to Germany from Poland in 1939 led to a campaign of genocide by 1941, Kershaw argued that the process was indeed "improvised genocide" rather than the fulfilment of a master plan. Kershaw views the Holocaust not as a plan, as argued by the intentionalists, but rather a process caused by the "cumulative radicalization" of the Nazi state as articulated by the functionalists. Citing the work of the American historian Christopher Browning in his biography of Hitler, Kershaw argues that in the period 1939–41 the phrase "Final Solution to the Jewish Question" was a "territorial solution", that such plans as the Nisko Plan and Madagascar Plan were serious and only in the latter half of 1941 did the phrase "Final Solution" come to refer to genocide. This view of the Holocaust as a process rather than a plan is the antithesis of the extreme intentionalist approach as advocated by Lucy Dawidowicz, who argues that Hitler had decided upon