URING the First World War, the French gradually developed a blockade policy aimed at the economic destruction of their Central Power opponents. Only gradually, and especially in retrospect, did they recognize that their wartime blockade policy had really been a programme of economic warfare-offensive economic measures designed to reinforce the more orthodox military tactics. Economic warfare procedures included those British maritime measures designed to keep overseas imports away from enemy or border neutral ports. They also encompassed such diplomatic blockade tactics as import consignment to private neutral societies, import rationing, and Allied preclusive purchases of neutral domestic products. A preclusive purchase involved a foreign buying operation whose primary objective was deprivation of the enemy rather than the satisfaction of the purchaser's domestic needs. Thus, hypothetically, goods which were totally useless to the buyer could be bought so as to keep them out of enemy hands. Generally, however, supply and preclusive purposes were not mutually exclusive. Implicit in the concept of preclusive buying was governmental rather than private initiative. Only the government could make the type of overall policy decisions which would waive normal financial considerations in the interest of wartime objectives. Clearly, private enterprises were guided by profit motives and thus sought to secure the most advantageous terms of sale. The government could weigh such normal commercial considerations as comparative product prices and transportation costs against denial to the enemy of key goods and hence a potential shortening of the war. It also could take into -account alternative uses for the same funds and decide whether a given outlay could be spent most usefully on a preclusive purchase, such as Dutch meat, or on an essential war material. It was also necessary to evaluate the effect of deprivation on the German economy and war-making potential and to ascertain whether Germany could procure the same goods or viable substitutes elsewhere. Such purchases could disrupt normal procurement patterns, since goods would be removed from markets to which the enemy had access (generally the neighbouring neutrals) rather than from those (generally overseas) where British maritime mastery made German activity almost impossible. Competition with Germany in neutral markets inevitably drove prices above world competitive levels and thus such operations could only be justified in long-range military rather than short-range financial terms. Since funds were not unlimited, a decision to implement a costly preclusive purchase meant that those funds would not be available for other wartime needs. The cost of fighting the war clearly exceeded many times over the expense of any given