, ▁allocated ▁these ▁aircraft ▁to ▁attack ▁the ▁Y ug oslav ▁capital ▁in ▁waves ▁by ▁day ▁and ▁night . ▁Lö hr ▁issued ▁his ▁orders ▁for ▁the ▁bomb ing ▁on ▁ 3 1 ▁March , ▁but ▁the ▁decision ▁to ▁bomb ▁Bel grade ▁would ▁not ▁be ▁confirmed ▁by ▁Hitler ▁until ▁ 5 ▁April . ▁Hitler ▁ordered ▁the ▁general ▁destruction ▁of ▁Bel grade , ▁but ▁at ▁the ▁last ▁minute ▁Lö hr ▁replaced ▁these ▁general ▁directions ▁with ▁specific ▁military ▁object ives ▁within ▁the ▁city . ▁ ▁On ▁ 3 ▁April , ▁Major ▁Vladimir ▁K ren ▁fle w ▁a ▁P ote z ▁ 2 5 ▁aircraft ▁to ▁Gra z ▁and ▁defect ed ▁to ▁the ▁Germ ans . ▁He ▁dis closed ▁the ▁locations ▁of ▁many ▁of ▁Y ug oslav ia ' s ▁dispers al ▁air fields , ▁as ▁well ▁as ▁codes ▁used ▁by ▁the ▁V V K J , ▁which ▁had ▁to ▁be ▁quickly ▁changed . ▁Also ▁dis closed ▁were ▁the ▁location ▁of ▁Y ug oslav ia ' s ▁tro op ▁mobil isation ▁cent res ▁and ▁air - raid ▁sh el ters ▁in ▁Bel grade . ▁On ▁the ▁afternoon ▁of ▁ 5 ▁April , ▁a ▁British ▁colon el ▁visited ▁M irk ović ▁at ▁the ▁V V K J ▁base ▁in ▁Z em un ▁and ▁informed ▁him ▁that ▁the ▁attack ▁on ▁Bel grade ▁would ▁commence ▁at ▁ 0 6 : 3 0 ▁the ▁next ▁day . ▁The ▁previous ▁day , ▁the ▁Y ug oslav ▁government ▁had ▁declared ▁Bel grade ▁an ▁open ▁city ▁in ▁the ▁event ▁of ▁host ilities . ▁The ▁German