The United States has maintained a stockpile of strategic and critical materials, primarily ores and minerals, since 1939. Since the end of the Cold War, the United States government has determined that most of the materials in the National Defense Stockpile (NDS) were excess to defense, industrial, and essential civilian needs, and has begun selling and otherwise disposing of most of the stockpiled materials. Recent concerns regarding the global availability of materials have caused a reexamination of the need for a stockpile and how the NDS might operate in order to serve the defense, industrial and essential civilian needs for materials.