Due to an increase in night attacks on bombers and training aircraft in the vicinity of aerodromes by enemy fighters, an Anti-Aircraft Mobile Force was formed in May 1941. This operation was known as ‘SCARECROW SCHEME’.
The force was to operate between dusk and dawn and was to cover the flare path of the aerodrome it assigned to cover. The force was to be moved from aerodrome to aerodrome daily or at intervals of several days. The force would operate under the orders of 2 AA Division and the aerodromes to cover would be made after consultation with Bomber and Fighter Command.
Initially the force comprised normally of six mobile searchlights with six four-wheeled searchlight generating lorries and a troop of Light Anti-aircraft guns (Bofors guns or a proportion of Bofors and Lewis or Bren guns). The searchlights were to be withdrawn form Cluster sites. “SCARECROW FORCE” was to operate independently of any Light anti-aircraft defences already sited for the defence of aerodromes. Communication would be made to the nearest searchlight site by field telephone which was connected direct to G.O.R. Each searchlight of the force was in touch with Force HQ by wireless. If “BARGAIN SCHEME” was ordered, the Light AA troop would move to its rendezvous allocated to it under “BARGAIN SCHEME”.
The scheme was soon extended to cover all aerodromes with searchlights which already had Bofors defence. The original force, with Light AA guns, was to remain separate and be known as “KING SCARECROW”. The new force would not be mobile but the searchlights would be based permanently at their allocated aerodrome. At night the Bofors at the aerodrome would come under the command of the officer appointed to command the SCARECROW FORCE at that aerodrome.
In January 1942 the Anti-aircraft forces known as “SCARECORW” were to be known as “CANOPY”. No standard layout was given for “CANOPY” as the conditions varied at each aerodrome. The layout would typically be in the form of an “L”, a straight line or a circle around the aerodrome. The layout decided would be made in consultation with the RAF Station Commander and the Ground Defence Officer. The policy of operation would also vary at each aerodrome. The officer commanding the Canopy Searchlights would obtain the policy form the RAF Station Commander and issue orders accordingly.
Searchlights and Bofors operating in the Gun Defeneded Areas of Yarmouth/Lowestoft and Harwich now also came under “CANOPY”. During 1942, in the Yarmouth/Lowestoft area, 12 search lights and 12 Bofors were operating to allow one Borfors and one searchlight to act as a team. These searchlights were known as CANOPY Searchlights. Other searchlights operating as part of the normal 6,000 yard layout were to be known as GDA searchlights.
Searchlights operating in the Yarmouth/Lowestoft GDA were to engage all hostile and unidentified aircraft at under 2,000 feet. Restrictions included “FIGHTERNIGHT” being ordered, if weather conditions were unsuitable for searchlights or if low cloud was present which would reflect the light and illuminate the target. Special cases of operation in GDA’s , for both CANOPY and GDA Searchlights were:
To render precise bombing impossible by blinding the pilot
To obscure the target under favorable conditions of low cloud or haze by exposing stationary or moving beams at a fixed pre-arranged angle or arc.
To mislead the enemy to his whereabouts or the whereabouts of the target in conjunction with dummy fires and gun flashes.
To tempt the enemy to avoid lighted areas and fly into unlighted areas covered by HAA guns.
“CANOPY” was also deployed at other vulnerable or sensitive areas. For example ORFORD CANOPY, consisting of 12 Bofors and 18 searchlights was deployed for protection of the new Battle Training area but was later withdrawn in November 1942.
2nd AA Division papers, TNA
41 AA Brigade papers, TNA
AADC Harwich papers, TNA