Base Defence Sectors


Base Defence Sectors were a relatively new formation within the RAF which was created as much for administrative purposes as military in order to face the challenges of equipping and protecting RAF bases overseas.   To date I have not found any official definition of a Base Defence Sector that can adequately and efficiently describe their function and the strength of each Sector.  However one of the best descriptions relating to the Base Defence Sectors that we are concerned with, is from the ORB Medical History of War written by Dr Richard Rycroft who was seconded to 21 BDS just before the invasion and below are the first two paragraphs of his report which gives a good picture of the complement structure of BDS.


No. 21. Base Defence Sector

1. Operational purpose of Unit.

Defence against night bombing of base during invasion of continent.  Threat from Luftwaffe has been considerably less than was expected.  Threat diminishes with the passing of each day and with the withdrawal of the German forces from France.


Unit is subdivided into:

(1).       Sector Headquarters. 42. Officers.  260.  O.R.

(2).       Five G.C.I. units, averaging 5 Officers. 80. O.R.

(3).       Many small signal units.  Ranging from 4 to 20 personnel on each unit.

(4).       I.M.R.U. 2. Officers. 30. O.R.

(5).       I.M.S.S.U.  4. Officers. 35. O.R.

(6).      1. Company of Air Formation Signals attached to Sector H.Q. 9. Officers. 249. O.R.


The composition of the Sector is constantly changing and small units move with great frequency and are therefore difficult to keep under medical supervision.  When first posted to this Sector the arrangements of units is almost too difficult to visualise.  Quite unlike any other branch of the R.A.F.


Conditions in France.  Sector H.Q. living in Chateau. (officers) and tents (men).  These were left by Germans who had headquarters in chateau.  Other units under canvas.  Widely dispersed from Sector H.Q. (2 to 100 miles).  Tendency for units to get further away from Sector H.Q.

Very hard to keep contact.


From the Official RAF History of Radar in the Second World War, we know that there were two major radar formations in Normandy: the 2nd Tactical Air Force tasked with moving forward from the beachhead in support of the army, eventually all the way across the Rhine and the Base Defence Sectors, one to cover the British beachhead in Normandy (No 24 BDS), another in support of the American landings and the build up across the beaches (No 21 BDS), and a third (No 25) a reserve sector, remaining in the UK until required.

On the next page you will see Appendix 42 which lists the Royal Air Force Radar Units Under The Allied Expeditionary Air Force June 1944.  This clearly lists the individual main units which made up 21 Base and its organisation structure up through 85 Group and towards this Second Tactical Air Force.  What this document does not show are the individual numbers for the 4 LWS (Small Light Warning Set) nor any of the supporting units which were subsequently added to the BDS’s as the invasion approached.  Fortunately we do have some further documentation which helps us build a picture of those units who were attached to 21 BDS and in particular those who made up the first echelon that landed on 6th June.

Further information on how the sector was formed and when can be gleaned in part of Dr Rycroft’s report called ” Medical history in War”.


2. Sector was formed at Church Fenton Yorkshire in January 1944.

Many of the constituent units had been formed since the previous year and were experienced in camp life under canvas.  There was only one move in England before the overseas move.  This was to Copley, nr Christchurch in England in 1944.  The movement to France was done in 3 main bodies – 1 GCI, and attached bodies (total 180 Officers, and O.Rs) landed on D-Day.  This unit was unfortunate in its location and lost approximately 25% of its strength – wounded and killed (11 x killed, 33 x wounded).  The loss in technical vehicles was even heavier and as a result this unit was unable to carry out the job it had been landed for.  Eleven further units landed on D+2 and had an uneventful landing except for a wetting due to inefficient landing craft command.  111 Sector Headquarters landed on about D+20.


3. Medical problems caused by preceding paragraphs

A Medical Officer was considered necessary for this unwieldy unit at the eleventh hour (previously the sick had been taken daily to the nearest RAF Station).  After two years as Squadron Medical Officer, a job that does not give one a command of paperwork and organisation, it was my lot to be chosen for this task.  I arrived at the unit, then at Sopley, nr Christchurch, on 23rd May 1944.  It is hard to be dispassionate about the conditions one found, especially since one was told a move into “concentration” was expected daily.  Briefly the facts were as follows:


Medical panniers were still in Equipment Section together with rest of Z1 equipment


Arrived on 24th May.  Unserviceable for 24 hours because of sign painting and removal of grease from body work


Hospital was being used by HQ as office tent.  This was only discovered after 4 days, and then by chance.  It was not considered worthwhile using this tent because of daily expectation of moving.  Small tents had not arrived.  One was borrowed for immediate use.

Leave a Reply

Your email address will not be published. Required fields are marked *