The overarching goal of this entire oversight structure was to enable the appropriate collection of foreign intelligence and counterintelligence, and to do so in a way that fully protected the rights and civil liberties of U.S. Persons.
The seminal document underpinning the intelligence oversight mission is Executive Order 12333, United States Intelligence Activities. This document, signed by President Ronald Reagan in 1981, was the third in a series of Executive Orders.
As a result of these executive orders, the Secretary of Defense directed establishment of an Inspector General for Intelligence in the Office of the Secretary of Defense. This office was assigned the mission of conducting independent oversight of all DoD intelligence activities. In November 1982, following the establishment of the DoD Inspector General, the Deputy Secretary of Defense directed that the Inspector General for Intelligence be redesignated as the Assistant to the Secretary of Defense (Intelligence Oversight) (ATSD (IO)).
In August 2014, as part of an ongoing reorganization to meet Secretary of Defense Guidance, the DoD realigned intelligence oversight functions under the Office of the Deputy Chief Management Officer (subsequently renamed the Chief Management Officer (CMO)) within the Office of the Secretary of Defense (OSD). The ATSD(IO) was renamed the Defense Senior Intelligence Oversight Official (SIOO) and was dual-hatted as the Deputy Director of Oversight and Compliance within the CMO.
In January 2020, Congress eliminated the position of the CMO and realigned all of the responsibilities assigned to the CMO to other OSD offices. During that realignment, the office of the ATSD(IO) was reconstituted and the SIOO was designated as the ATSD(IO).
In September, 2021, in an effort to improve DoD’s overall efforts to protect privacy and civil liberties and to enhance DoD’s ability to provide effective independent oversight, the Deputy Secretary of Defense directed the merger of all privacy, civil liberties, and transparency functions with the intelligence oversight functions and redesignated the ATSD(IO) as the ATSD for Privacy, Civil Liberties, and Transparency (ATSD(PCLT)). The position of the SIOO was regenerated and the SIOO was dual-hatted as the Principal Deputy ATSD(PCLT). In the process, the oversight functions the ATSD(IO) performed were aligned in a directorate within OATSD(PCL) formally designated as the Intelligence Oversight Directorate.
On December 23, 2024, with the approval of the Servicemember Quality of Life Improvement and National Defense Authorization Act for Fiscal Year 2025 (FY2025 NDAA), Congress directed formal establishment of the SIOO position as a matter of law. In accordance with the FY2025 NDAA, the SIOO is responsible for independent oversight of all intelligence, counterintelligence, and intelligence-related activities of the Department of Defense and shall have such other related responsibilities as may be determined by the Secretary.
The DoD SIOO is located within the OATSD(PCLT) and now, by law, has direct access to the Secretary of Defense and the Deputy Secretary of Defense as well as access to any information necessary for perform the duties of the SIOO.
The SIOO reports on Intelligence Oversight activities at least quarterly, along with reporting directly to the Intelligence Oversight Board (IOB), a standing committee of the President's Foreign Intelligence Advisory Board (PIAB).