Resort to emergency powers has become a major political and legal issue since 2001, generating intense public debate and opposition as well as academic attention. One lesson of history is that emergency powers are often associated with war. Jack L. Goldsmith argued that the September 11, 2001 attacks created a 'national emergency' that justified ignoring civil liberties. Gross and Ni Aolain excluded from their study emergencies that arise from economic crises as well as natural disasters, confining their attention to 'violent crises' such as wars, international armed conflicts, rebellions and terrorist attacks. Carl Schmitt's ideas dovetailed with the ruthless and cynical exploitation of presidential emergency powers, starting in 1919 with the social Democrat Friedrich Ebert, the first Weimar president. He considered liberalism, particularly as manifested in the Weimar Constitution, to be inadequate to the task of protecting state and society menaced by the great threat of another communist-led revolution by the working class.