This volume, the first of seven in the army series of the official history of Australia in the war of 1939-45, carries the story of the Second AIF up to the end of the operations in Cyrenaica in the first quarter of 1941. It tells briefly the story of the Australian Army from 1919 to 1939 and describes the raising of an expeditionary force for service in Hitler's war. It discusses some of the problems encountered by the commanders of that force in the Middle East in 1940 - often problems of enduring interest in that they have been met and will be met again by other leaders of the forces of minor partners in a coalition war. The defeat of the Italian army in Cyrenaica by the 7th Armoured and 6th Australian Divisions is narrated in a degree of detail made possible by reliance not only on contemporary reports and war diaries but on private papers and interviews and correspondence with a large number of participants. Finally the question whether the British political leaders in February 1941 missed a golden opportunity of marching on to Tripoli and securing great strategical gains is examined in the light of hitherto unpublished documents from both the Allied and the Axis side.