- f ight ing ▁techniques ▁changed ▁little ▁until ▁just ▁prior ▁to ▁World ▁War ▁II . ▁ ▁In ▁the ▁meant ime , ▁aircraft ▁performance ▁had ▁improved ▁trem end ously ; ▁compared ▁to ▁World ▁War ▁I ▁versions , ▁modern ▁bom bers ▁could ▁fly ▁about ▁twice ▁as ▁fast , ▁at ▁over ▁twice ▁the ▁alt itude , ▁with ▁much ▁greater ▁bomb ▁loads . ▁They ▁fle w ▁fast ▁enough ▁that ▁the ▁time ▁between ▁detect ing ▁them ▁and ▁the ▁bom bers ▁reaching ▁their ▁targets ▁left ▁little ▁time ▁to ▁launch ▁intercept ors ▁to ▁shoot ▁them ▁down . ▁Ant ia ircraft ▁guns ▁were ▁similarly ▁affected ▁by ▁the ▁alt itudes ▁at ▁which ▁they ▁fle w , ▁which ▁required ▁extremely ▁large ▁and ▁heavy ▁guns ▁to ▁attack ▁them , ▁which ▁limited ▁the ▁number ▁available ▁to ▁the ▁point ▁of ▁being ▁rendered ▁imp ot ent . ▁At ▁night , ▁or ▁with ▁limited ▁visibility , ▁these ▁problems ▁were ▁comp ounded . ▁The ▁w ides p read ▁conclusion ▁was ▁that ▁" the ▁bom ber ▁will ▁always ▁get ▁through ", ▁and ▁the ▁Royal ▁Air ▁Force ▁inv ested ▁almost ▁all ▁of ▁their ▁efforts ▁in ▁developing ▁a ▁night ▁bom ber ▁force , ▁with ▁the ▁Central ▁F lying ▁School ▁responsible ▁for ▁one ▁of ▁the ▁most ▁important ▁develop ments ▁in ▁the ▁period ▁by ▁introdu cing ▁" bl ind ▁flying " ▁training . ▁ ▁The ▁Spanish ▁Republican ▁Air ▁Force ▁used ▁some ▁Pol ik arp ov ▁I - 1 5 s ▁as ▁night ▁f igh ters . ▁Pil ot ▁José ▁Fal c ó ▁had ▁equ ipped ▁his ▁f ighter ▁with ▁a ▁radio ▁receiver ▁for ▁land