During a time of war, countries like the United States tried to get the most out of the materials within their society. For example, the US faced a metal shortage in the beginning of World War II. Their campaign to collect scrap metal from citizens helped to ensure that they had the necessary materials to create military weapons and ammunition.
Along with scrap collection, citizens also bought war bonds or planted victory gardens. War bonds helped the federal government to raise money for the war effort and victory gardens helped to supply additional food for soldiers.