Final answer:
Military specifications (mil-spec) describe the essential technical requirements for purchasing uniquely military or substantially modified commercial items. Weapon builders need assurance of supply for these items in wartime, which affects design decisions. The U.S. Defense National Stockpile Center maintains material reserves to support military needs.
Step-by-step explanation:
The essential technical requirements for purchasing material that is military unique or substantially modified commercial items are described by military specifications. Military specifications, commonly known as mil-spec, are a set of standards used to describe the physical and functional properties that military equipment and products must meet. It is crucial for weapon builders to be confident in the continuous availability of key products during wartime, which can influence the design and procurement of military technology and materials.
To mitigate supply risks, countries such as the United States may build reserves of critical materials through entities like the U.S. Defense National Stockpile Center, which maintains stockpiles from aluminum oxides and bauxite to tungsten and zinc, although these reserves are not infinite and may be reduced over time. This forms a part of a broader strategy to ensure that national security is not compromised due to reliance on foreign imports for key technologies and materials necessary for defense systems.