Most international historians present the outbreak of World War II as the result of an irreconcilable conflict between Great Britain and Germany. This ubiquitous Anglo-German perspective fails to recognize complex causes and repercussions of international events, misappropriates historical responsibilities, and overlooks many global and imperial factors of the war's origins. Reynolds M. Salerno shows that the situation in the Mediterranean played a decisive role in the European drama of the late 1930s and profoundly influenced the manner in which the Second World War unfolded. Vital Crossroads is the result of the author's remarkable access to and extensive research in twenty-eight archives in five different countries.

Concentrating on the period from the Mediterranean crisis of 1935 to Italy's declaration of war in June 1940, Salerno demonstrates that the international politics of pre-World War II Europe-particularly in the Mediterranean-can only be understood as the multilateral interaction of British, French, German, and Italian foreign and defense policies. Control of the Mediterranean, he asserts, was a central concern for the European powers in 1935-40, and a fundamental reason why Europe went to war and why the conflict unfolded as it did. As a result, France and Italy influenced and often determined the nature and direction of Allied and Axis policy to an extent disproportionate to their nations' military and economic strength.

Salerno contends that the Allies' reluctance to take decisive action against Fascist Italy in 1939-40 contributed to the fall of France in 1940, Britain's desperate situation in 1940-41, and the post-war collapse of Britain as a world power. At a time when the Allied powers dreaded the ability of the German military to march across the European continent, they also feared that the Italian armed forces would strive to fulfill Mussolini's grand imperial ambitions in the Mediterranean.