Russia has the world’s largest stocks of weapon-usable fissile materials. Most of this material is a legacy of the Cold War, when the Soviet Union and the United States each created nuclear industries sized to produce tens of thousands of nuclear weapons. Significant quantities of weapon-grade material also are present on the civilian side of nuclear complex, in storage, or being transferred from one facility to another, or used for research and other purposes. Providing security for all this material will continue to be a major task for Russia for decades.