Individual collections range in size from a single file to the 1000 boxes of Captain Sir Basil Liddell Hart's papers.
To these are now being added research materials, notably interview transcripts, collected in connection with television documentaries and academic projects.
The scope of the holdings is vast, from high level defence policy and strategic planning as, for example, in the papers of Field Marshal Alan Brooke, 1st Viscount Alanbrooke and General Hastings Lionel Ismay, 1st Baron Ismay down to the command of individual units in the field.
Many significant collections reflect the revolution in weapon technology in the 20th century and the re-evaluation of tactics and strategy which necessarily followed on from the invention of the tank and the development of air power.
The Centre's web site hosts the Location Register of Twentieth Century Defence Personnel, a database of some 3000 British defence personnel who achieved the ranks above and including Major General, Air Vice Marshal and Rear Admiral between the years 1900-1975.