/ 1 3 ▁April ▁bom bed ▁the ▁railway ▁mar sh alling ▁yards . ▁Other ▁similar ▁targets ▁in ▁Bulg aria ▁were ▁attacked ▁by ▁the ▁R AF ▁during ▁the ▁B alk ans ▁Camp aign . ▁ ▁After math ▁and ▁legacy ▁▁ ▁The ▁bomb ing ▁of ▁Bel grade ▁par al ys ed ▁communic ations ▁between ▁the ▁Y ug oslav ▁military ▁and ▁its ▁headquarters , ▁and ▁contributed ▁decis ively ▁to ▁the ▁rapid ▁collapse ▁of ▁Y ug oslav ▁resistance . ▁Civil ian ▁cas ual ties ▁were ▁significant , ▁but ▁sources ▁vary ▁widely ▁from ▁ 1 , 5 0 0 ▁to ▁ 1 7 , 0 0 0 ▁killed . ▁They ▁were ▁w ors ened ▁by ▁the ▁dis closure ▁of ▁air - raid ▁shelter ▁locations ▁to ▁the ▁Germ ans ▁in ▁the ▁days ▁preceding ▁the ▁attack . ▁The ▁official ▁cas ual ty ▁figure ▁released ▁by ▁the ▁occupation ▁authorities ▁soon ▁after ▁the ▁bomb ing ▁was ▁ 2 , 2 7 1 ▁killed . ▁Other ▁sources ▁mention ▁ 5 , 0 0 0 ▁to ▁ 1 0 , 0 0 0 ▁fatal ities , ▁and ▁later ▁Y ug oslav ▁estimates ▁r anged ▁even ▁higher . ▁The ▁historian ▁J oz o ▁Tom ase v ich ▁writes ▁that ▁the ▁higher ▁estimates ▁were ▁down grad ed ▁following ▁" care ful ▁post war ▁investig ations ", ▁and ▁indicates ▁that ▁a ▁figure ▁between ▁ 3 , 0 0 0 ▁and ▁ 4 , 0 0 0 ▁is ▁more ▁real istic . ▁ ▁Bel grade ▁was ▁occupied ▁on ▁ 1 3 ▁April ▁ 1 9 4 1 ,