The Space Development Agency (SDA) began as a directorate of the United States Department of Defense's office of the under secretary of defense for research and engineering (OUSD (R&E)) which supports space development in the interests of U.S. national security. The SDA was conceived by Mike Griffin and established in 2019 after his appointment to USD (R&E) early in the Trump Administration. A top priority is to implement the National Defense Space Architecture (NDSA), using spiral models for its development method. While initial leadership sought more aggressive capabilities including space-based interceptors similar to the Strategic Defense Initiative, the Biden Administration has since refocused on sensing and arms control.