Documents
Documents have provided the majority of data collected so far and are the foundation upon which the entire project has been built.
The National Archives
The documents include War Diaries, Operation Orders and Defence Schemes that were compiled by the military formations that occupied East Sussex 1940-41 and made available for public inspection at The National Archives (TNA).
War Diaries
War diaries were compiled by every military unit from the point they were mobilised for war; their basic purpose was to provide an account of the unit's day-to-day activities. Those compiled by units in Home Forces are filed in TNA's WO 166 series.
The usefulness of diaries varies enormously; while some faithfully record every pillbox completed or every enemy aircraft spotted and bombs dropped by the hour, others provide only a weekly/monthly list of which officers are on leave or have been transferred to/from other units.
Other problems include missing sections (or whole unit diairies) and while some diaries are typed and easy to read, others are handwritten, and in many cases are not easily read.
My journey through war diaries began by looking at those of the Royal Engineers units of 45 Division that would have been involved with the construction of the defences. I have gradually moved through the entire division, seeking out those diaires that still exist, as well as those of supporting formations such as Coast Artillery. The process has moved onto the diaries of the divisions that subsequently defended East Sussex.
Operation Orders
Operation Orders (seemingly also known as Operational Memoranda and Operation Instructions) are often found filed amongst the pages of war diaries; these, as their names suggest, set out 'policy', and can range to regulations regarding the carriage of arms and ammunition when off duty, changes in formation/command or detailed instructions of a unit's move to its next base of operations.
Operation orders can also be defence schemes.
Defence Schemes
As mentioned above, defence schemes are sometimes issued as operation orders, sometimes not. A defence scheme is exactly as its name implies; it describes the ways and means that the area it covers is to be defended.
Schemes were compiled at all levels; hidden among the diaries of WO 166 the historian will find schemes at divisional, brigade (sub-area), battalion (sector) and occasionally down to company or small defended locality level.
The further down this heirarchy you move, theoretically, the more detailed the scheme may be. Divisional schemes examine the wider picture of the division's area, including topography, areas of responsibility (e.g. infantry brigade sub-areas, Home Guard areas) and major defensive features; individual pillboxes are not listed.
A divisional area was broken down into sub-areas and sub-sectors (this terminology changed in 1941); a sub-area was that zone defended by an infantry brigade, and this was broken down into sub-sectors, usually centred around a major coastal town such as Newhaven and Eastbourne.
Sub-area schemes usually provide more detail than a divisional scheme for its particular area, and can give details of individual defence works.
Sub-sector schemes discuss their particular town and its surrounding nodal points, although the latter theoretically had their own schemes too.
I've used the word 'theoretically' a lot here, as there are no hard and fast rules as to the level of detail given; some formations were much better at providing detailed plans than others.
Local Documentary Sources
An as yet untapped source has been the East Sussex Record Office (ESRO) in Lewes; I know that there are documents relating to the Home Guard and defence issues amongst the holdings. My research at TNA has been so successful that to date I have not yet found the time to begin my local research.
German Intelligence Documents
There appears to be a considerable amount of German intelligence material gathered as part of Operation Sealion; this includes aerial photographs and maps of the defences, copies of which survive in various collections in the UK.
The German High Command obviously needed accurate maps for invasion, and, being practical people, did the sensible thing and used existing Ordnance Survey maps!
The Abteilung für Kriegskarten und Vermessungswesen (Department of Military Maps and Surveying) took the standard Ordnance Survey series and rescaled them to German metric standards.
Maps were then issued in several series with different data overlays according to their needs.
A strong advantage of using German sources is that the German High Command had a vested interest in recording as many defences as possible. It is hoped that these sources will fill in many gaps in British sources.
It is anticipated that German intelligence material will contain oversights and misinterpretation. However, careful cross-referencing between sources may indicate how accurate German interpretation of reconnaissance data really was.