es ign ated ▁as ▁reg iments ▁from ▁January ▁ 1 9 3 9 ) ▁formed ▁part ▁of ▁ 4 7 ▁AA ▁Brigade ▁in ▁ 5 th ▁AA ▁Division , ▁which ▁had ▁the ▁responsibility ▁for ▁def ending ▁South am pton . ▁In ▁February ▁ 1 9 3 9 ▁the ▁UK ' s ▁AA ▁def ences ▁came ▁under ▁the ▁control ▁of ▁a ▁new ▁Anti - A ircraft ▁Command . ▁In ▁June ▁a ▁partial ▁mobil isation ▁of ▁the ▁T A ▁was ▁begun ▁in ▁a ▁process ▁known ▁as ▁' cou vert ure ', ▁where by ▁each ▁AA ▁unit ▁did ▁a ▁month ' s ▁tour ▁of ▁duty ▁in ▁rotation ▁to ▁man ▁selected ▁AA ▁and ▁search light ▁positions . ▁On ▁ 2 4 ▁August , ▁ahead ▁of ▁the ▁declaration ▁of ▁war , ▁AA ▁Command ▁was ▁fully ▁mobil ised ▁at ▁its ▁war ▁stations . ▁The ▁' Ph oney ▁war ' ▁that ▁followed ▁was ▁an ▁opportunity ▁for ▁training ▁and ▁equ ipping ▁the ▁AA ▁def ences . ▁In ▁June ▁ 1 9 4 0 ▁the ▁RA ' s ▁AA ▁reg iments ▁were ▁designated ▁He avy ▁AA ▁( H AA ) ▁to ▁distinguish ▁them ▁from ▁the ▁new ▁Light ▁AA ▁( LA A ) ▁units ▁being ▁formed . ▁ ▁Battle ▁of ▁Britain ▁ ▁After ▁the ▁British ▁army ' s ▁ev acu ation ▁from ▁D unk irk , ▁the ▁South ▁Coast ▁ports ▁such ▁as ▁South am pton ▁and ▁Port sm outh ▁became ▁prime ▁targets ▁for ▁attacks ▁by ▁the ▁German ▁Luft wa ffe ▁in ▁the ▁so - called ▁' Channel ▁Batt les ' ▁that ▁preced ed