Congress has an essential role to reduce nuclear risk. To address nuclear threats short of military force, the United States employs arms control, nonproliferation, nuclear security, and unilateral steps (i.e., without relying on other countries). Arms control involves agreements with other countries that have nuclear weapons to reduce the risk of nuclear war by placing limits on nuclear weapons and delivery vehicles (e.g., New START). Nonproliferation involves efforts to limit the spread of nuclear weapons and prevent more states from acquiring them. Nuclear security involves efforts to prevent nuclear weapons components from being stolen or from sabotage, or nuclear materials used for peaceful purposes from being stolen and turned into nuclear weapons.