With the fall of France, Hitler was left with only one enemy between himself and the permanent establishment of his domination in Europe. Britain had suffered serious losses, both political and military: its chief strength lay in its economic resources and insular position. Already, in Directive No. 9, Hitler had laid down the lines of his war on Britain's economy. On 26th May, with almost all Norway effectively occupied, and German troops in control of Holland and Belgium, a Supplement to that Directive was issued by Keitel. It ordered attacks on British food supplies whose destruction is of vital importance in breaking the will to resist, the interruption of public services (gas, water, and electricity), and, above all, the destruction of the aircraft industry in order to deprive the English Air Force, the last weapon which can be directly used against us, of the basis of its existence. Now Hitler saw the prospect of a frontal attack on the island. On 2nd July, 1940, he decided that a landing in England was possible, provided that air superiority can be attained and certain other necessary conditions fulfilled, and he asked for reports from the three services. As yet, he made clear, the plan to invade England has not taken any definite shape: his preparations were only for a possible operation; but a fortnight later he had reached more positive conclusions.