The article deals with the period of formation of the state of Iraq. A peculiar combination of the features of political development, characterized by a complex interweaving of social, national and religious components, along with international factors of a regional and strategic levels, put Iraq among the countries whose development is of great scientific and practical interest. The identification and study of the historical roots, specific factors and developmental features of Iraq allows us to advance further in exploring the nature of the events and phenomena taking place in this country, to further understand the essence of numerous regional problems and political processes in the Middle East. A special place in the present work is given to the analysis of the role and interests of Great Britain in the process of birth and evolution of this Arab state. Having proclaimed Mandate in 1920 in Mesopotamia, the British government initiated a process of state building and territorial formation of the country, a search for an acceptable political system capable to ensure the necessary balance between the imperial requests of Great Britain and the movement of Iraq towards independence and sovereignty. The work examines the influence of Great Britain on the process of territorial formation of Iraq, considers other motives and grounds that had an impact on the emergence of this state.