A National Cyber Defense Center (NCDC) would plan and coordinate US government cyber defense operations below the threshold of armed conflict while also conducting contingency planning, and if necessary coordinating national cyber defense operations in the event of armed conflict. The center would plan and coordinate across four key lines of operation, which are essential both below the level of armed conflict and in crisis or war: cyber deterrence, active cyber defense, offensive cyber operations in support of defense, and cyber incident management. To be most effective, the NCDC should be placed in the Office of the National Cyber Director (ONCD), which was established by Congress in late 2020 as a new element of the Executive Office of the President.