▁Soviet ▁plans ▁to ▁build ▁an ▁atomic ▁bomb ▁became ▁known ▁in ▁the ▁west ▁in ▁ 1 9 4 8 , ▁this ▁project ▁was ▁still ▁long ▁from ▁being ▁ready ▁to ▁produce ▁even ▁a ▁prototype , ▁and ▁in ▁March ▁ 1 9 4 9 , ▁they ▁started ▁development ▁of ▁the ▁North ▁American ▁F - 8 6 D ▁Sab re ▁and ▁Lock he ed ▁F - 9 4 ▁Star fire ▁as ▁stop - g ap ▁measures . ▁All ▁of ▁them ▁entered ▁service ▁around ▁the ▁same ▁time ▁in ▁the ▁early ▁ 1 9 5 0 s . ▁In ▁the ▁Korean ▁War , ▁after ▁Star f ires ▁proved ▁in effect ive , ▁Marine ▁Corps ▁Douglas ▁F 3 D ▁Sky kn ights ▁shot ▁down ▁six ▁aircraft , ▁including ▁five ▁M iko yan - G ure v ich ▁Mi G - 1 5 s ▁without ▁loss , ▁as ▁the ▁Mi G - 1 5 s ▁lack ed ▁rad ar ▁to ▁shoot ▁down ▁individual ▁f igh ters , ▁though ▁they ▁were ▁effective ▁against ▁bom ber ▁form ations ▁at ▁night . ▁ ▁The ▁R AF ▁began ▁studies ▁into ▁new ▁f ighter ▁designs ▁in ▁the ▁immediate ▁post war ▁era , ▁but ▁gave ▁these ▁projects ▁relatively ▁low ▁priority . ▁By ▁the ▁time ▁of ▁the ▁Soviet ▁bomb ▁test , ▁the ▁night - fig h ter ▁design ▁was ▁still ▁strictly ▁a ▁paper ▁project , ▁and ▁the ▁existing ▁Mos qu ito ▁fleet ▁was ▁generally ▁unable ▁to ▁successfully ▁intercept ▁the ▁T up ole v ▁Tu - 4 ▁bom ber ▁it ▁was ▁expected ▁to ▁face . ▁This ▁led ▁to ▁r