Upon the outbreak of hostilities on 3 September 1939, Britain and France enacted a repeat of the German naval blockade used to great effect throughout the previous war. They were able to do this because they had vastly more powerful naval forces at their disposal than Germany, a country lacking in natural resources and heavily reliant on large scale imports of a wide range of goods. Perhaps the material Germany needed above all others was iron ore, a steady supply of which was imperative in the creation of steel to sustain its war effort and general economy.