The second example of historical sociology is the work of Michael Mann.Mann is invovled in a four volume study of the sources of social power dealing with the whole of human history. this is an enormously ambitious project aimed at showing just how states have taken the forms that they have.In the words, Mann studies the ways in which the various forms of power have combined in specific historical circumstances.He makes a major contribution to our thinking of how states have come into existence and abuot how they have related to the international political system. In this sense his work is similar to that of Tilly, but the major innovation of Mann's work is the he has developed a sophisticated account of the forms of power that combine to form certain types of states.This is his IEMP model.The argument is summarized in Box 12.1 to give you an idea of its potential to shed light on how the state has taken the form that it has throughout history. It should make you think that the version of the state presented by neo -realism is very simple,but note also that there is some overlap between the focus of neo -realism on war and the focus of historical sociology on hoe states class, and war interact.