The thesis examines the three levels in which fascist expansionism was expressed - expansion as ideology; expansion and foreign policy-making; expansion as a joint enterprise for a fascist new order. On the level of ideology, it examines the ideological traditions in the Italian and German post-unification societies and shows how fascist ideology achieved an ideological fusion of pre-existing radical traits in a new synthesis with an increased emphasis on action and a determination to unite reality with utopia. It also studies the expansionist ideologies of the two fascist movements-regimes as coherent systems of thought, with a number of similar underlying features (historic living space, elitism, cult of violence, unity of thought and action) which explain the rigidity and dynamism of the expansionist arguments in Italian and German fascism. On the level of foreign policy-making, the thesis analyses the domestic framework of foreign-policy making and assesses the success of the two regimes' efforts to produce conditions conducive to the realisation of their large-scale expansionist visions. It lays emphasis on the leader-oriented character of the two fascist systems, which led to the relegation of other powerful groups (traditional élites, fascist parties) to a functional status subject to the will of the leader. It also examines the practical forms of the two regimes' expansionist foreign policy (i.e. revisionism, colonialism, irredentism) and shows how ideology provided only a long-term framework for expansion. Lack of clear, short- and medium-term strategies rendered the fascist foreign policies extremely flexible and opportunistic, alert to external opportunities and unbound by prior commitments. On the level of interaction, the thesis emphasises the neglected importance of the exclusive relation between the two fascist regimes for the radicalisation of their expansionist policies in the second half of the 1930s. It examines the process of fascism's internationalisation and analyses how both rivalry and co-operation between the two fascist regimes contributed to the radicalisation of their expansionist objectives and policies. War accentuated all the above tendencies and aspirations of the two fascist regimes. In 1940-41 they embarked upon the realisation of their extreme expansionist visions in a final attempt to unite reality with utopia. Failure, however, to balance means with ends and to achieve an effective form of domestic and international co-ordination transformed an ideological campaign into desperate war-making, pushing fascism to its eventual collapse in 1943-45.