The U.S. Space Force (USSF) is the newest branch of the Armed Forces, established December 20, 2019 with enactment of the Fiscal Year 2020 National Defense Authorization Act. The USSF was established within the Department of the Air Force, meaning the Secretary of the Air Force has overall responsibility for the USSF, under the guidance and direction of the Secretary of Defense. Additionally, a four-star general known as the Chief of Space Operations (CSO) serves as the senior military member of the USSF and is a member of the Joint Chiefs of Staff.