Preclusive purchasing is an economic warfare

Economic warfare

Economic warfare is the term for economic policies followed as a part of military operations during wartime.The purpose of economic warfare is to capture critical economic resources so that the military can operate at full efficiency and/or deprive the enemy forces of those resources so that they...

 tactic where one belligerent in a conflict purchases matériel and operations from neutral countries

Neutral country

A neutral power in a particular war is a sovereign state which declares itself to be neutral towards the belligerents. A non-belligerent state does not need to be neutral. The rights and duties of a neutral power are defined in Sections 5 and 13 of the Hague Convention of 1907...

 not for domestic needs, but in order to deprive other belligerents their use. The tactic was pioneered by the French in World War I.

Preclusive purchasing drives up the price by shifting the demand curve

Demand curve

In economics, the demand curve is the graph depicting the relationship between the price of a certain commodity, and the amount of it that consumers are willing and able to purchase at that given price. It is a graphic representation of a demand schedule...

 out.

Preclusive purchasing was used by the British during World War II in order to deny Nazi Germany

Nazi Germany

Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...

 access to Spanish Wolframite

Wolframite

Wolframite WO4, is an iron manganese tungstate mineral that is the intermediate between ferberite and huebernite . Along with scheelite, the wolframite series are the most important tungsten ore minerals. Wolframite is found in quartz veins and pegmatites associated with granitic intrusives...

. Similarly, the British and Americans bought chromite

Chromite

Chromite is an iron chromium oxide: FeCr2O4. It is an oxide mineral belonging to the spinel group. Magnesium can substitute for iron in variable amounts as it forms a solid solution with magnesiochromite ; substitution of aluminium occurs leading to hercynite .-Occurrence:Chromite is found in...

 ore from Turkey, to reduce Turkey's ability to supply that mineral to Germany; as part of the "package deal", the Anglo-Americans had to buy Turkish dried fruit and tobacco as well.

In the period prior to the Attack on Pearl Harbor

Attack on Pearl Harbor

The attack on Pearl Harbor was a surprise military strike conducted by the Imperial Japanese Navy against the United States naval base at Pearl Harbor, Hawaii, on the morning of December 7, 1941...

 while the United States was officially neutral, the United States began to preclusively purchase Chilean copper and Brazilian manganese

Manganese

Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...

, rubber

Rubber

Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...

, industrial diamonds, quartz crystal, and mica

Mica

The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition...

.