This series consists chiefly of Reports and appreciations on the defence of coasts and fortresses at home and overseas, prepared for the Director. They have been collected from a variety of sources, and the majority date from the 1930s and 1940s.
The series also includes trials reports of equipment carried out and originated by the School of Artillery, Larkhill.
The series includes material which would otherwise be found amongst the Records of the Chief of the (Imperial) General Staff and its directorates (WO).