The Research Institute of National defence also known as the National Defence Research Institute (FOA) was established in 1945, and took over operations at the Armed Forces Chemical Institute (Försvarsväsendets kemiska anstalt, FKA), the Institute of Military Physics (Militärfysiska institutet, MFI) and the Swedish Board of Inventions telecommunications technical working group (Statens uppfinnarnämnds teletekniska arbetsgrupp, SUN). The FOA was organized in three research departments, FOA 1 chemistry/medicine, FOA 2 general physics and FOA 3 telecommunications and an office.

In 1959 FOA 4 (nuclear physics and nuclear chemistry) was added. A special institution for operations analysis, planning and investigation FOA P, was added in 1958 and was renamed the planning agency in 1962. In 1958 the office was reorganized into the administrative bureau. In 1962, an institution for materials research was added and in 1965 the Defence Telecommunications Technology Laboratory (Försvarets teletekniska laboratorium) was separated from the FOA 3 as a separate unit.

A major reorganization occurred on 1 July 1974. After this the FOA was organized in a central office, which accounted for among other thing the projections, management, staffing and education issues, and five main departments, FOA 1-5:

FOA 1: armed forces studies, environmental and social studies, security policy and operations analysis and systems analysis

FOA 2: general physics, nuclear device technology, EDP, material research, protection technology, etc.

FOA 3: optics, electronics, acoustics, radar and signals intelligence

FOA 4: biochemistry, microbiology, chemistry and radiac

FOA 5: behavioral sciences, biotechnology and medicine

The central office was divided in 1976 into three parts: central planning, administrative bureau and staff administrative bureau. These were later reorganized into two: the Planning and development unit and the management unit.

Together with the National Aeronautical Research Institute (FFA) the new agency Swedish Defence Research Agency (FOI) was established on 1 January 2001.