▁aer ial ▁phot ography . ▁The ▁aircraft ▁paid ▁particular ▁attention ▁to ▁the ▁villages ▁of ▁Prin avor ▁and ▁Tr n ini ć ▁B rij eg ▁where ▁the ▁British ▁military ▁mission ▁and ▁American ▁military ▁personnel ▁were ▁located . ▁This ▁was ▁observed ▁by ▁Street , ▁the ▁acting ▁commander ▁of ▁the ▁British ▁military ▁mission , ▁who ▁assumed ▁it ▁was ▁spot ting ▁for ▁a ▁bomb ing ▁ra id ▁and ▁ad vised ▁both ▁T ito ▁and ▁the ▁Americans . ▁Both ▁Al lied ▁miss ions ▁moved ▁their ▁locations ▁as ▁a ▁result . ▁ ▁Despite ▁the ▁intelligence ▁received ▁and ▁observations ▁made ▁by ▁the ▁British , ▁the ▁Part is ans ▁appear ▁to ▁have ▁been ▁quite ▁compla cent ▁about ▁the ▁threat , ▁with ▁T ito ' s ▁chief ▁of ▁staff , ▁Ar so ▁J ovan ović , ▁swe aring ▁that ▁" a ▁German ▁attack ▁was ▁impossible ". ▁The ▁most ▁obvious ▁indicator ▁that ▁T ito ▁was ▁una ware ▁of ▁the ▁im min ent ▁attack ▁is ▁that ▁he ▁remained ▁at ▁the ▁Dr var ▁cave ▁over night ▁on ▁the ▁evening ▁of ▁ 2 4 ▁May , ▁following ▁a ▁celebr ation , ▁instead ▁of ▁returning ▁to ▁Bast asi . ▁ ▁Through ▁Ult ra ▁intercept s ▁of ▁German ▁signal ▁traffic , ▁the ▁British ▁had ▁become ▁aware ▁that ▁the ▁Germ ans ▁were ▁planning ▁an ▁operation ▁c oden amed ▁" R ö ss els pr ung " ▁but ▁the ▁information ▁available ▁did ▁not ▁include ▁where ▁the ▁operation ▁would ▁occur ▁or ▁what ▁its ▁object ives ▁might ▁be . ▁ ▁Pl anning ▁Following ▁intelligence ▁collection , ▁higher ▁level ▁planning ▁for ▁the ▁operation