Ideas and leaders matter. Fascism's syncretic ideology is crucial to understanding its rise and support. So too is the coterie charisma exerted by leaders like Hitler over an inner core even in the wilderness years; his centripetal charisma went on to help attract the masses to the ‘Führer party’ for very diverse reasons; and the cultic charisma leaders developed especially when in power further helps explain their appeal. The four dark sides of nationalism – namely, its ethnic, religious, scientific and economic dimensions – are also crucial to understanding genocide. So too is leadership: no Hitler, no Holocaust. Genocide also points to the importance of lower levels of leaders, who were sometimes influenced by the charisma of the ‘great’ leader, although in other cases, such as Milosevic's Serbia, the charismatisation of the national idea was more influential.