▁ ▁and ▁their ▁aircraft ▁units . ▁Later ▁that ▁spring , ▁a ▁number ▁of ▁destroy ers ▁were ▁added . ▁On ▁ 1 0 ▁April ▁ 1 9 4 1 , ▁Second ▁K ō k ū ▁Sent ai ▁compr ised ▁, ▁ ▁and ▁the ▁ 2 3 rd ▁K uch ik ut ai ▁( Dest roy er ▁Unit ). ▁Four th ▁K ō k ū ▁Sent ai ▁consisted ▁sole ly ▁of ▁light ▁car rier ▁ ▁and ▁her ▁aircraft ▁unit , ▁until ▁two ▁destroy ers ▁were ▁added ▁in ▁August . ▁( At ▁its ▁in ception , ▁First ▁Air ▁Fle et ▁did ▁not ▁include ▁Third ▁K ō k ū ▁Sent ai ▁and ▁it ▁did ▁not ▁include ▁it ▁on ▁ 7 ▁December ▁ 1 9 4 1 . ▁Third ▁K ō k ū ▁Sent ai ▁( 3 rd ▁Car rier ▁Division , ▁see ▁table ▁below ) ▁was ▁attached ▁to ▁First ▁Fle et , ▁as ▁distinct ▁from ▁First ▁Air ▁Fle et . ▁On ▁ 1 ▁April ▁ 1 9 4 2 , ▁Third ▁K ō k ū ▁Sent ai ▁was ▁dis band ed .) ▁See ▁the ▁table ▁titled ▁" Trans ition ", ▁below . ▁ ▁When ▁formed ▁on ▁ 1 0 ▁April ▁ 1 9 4 1 , ▁First ▁Air ▁Fle et ▁was ▁a ▁naval ▁battle group ▁with ▁the ▁single ▁most ▁powerful ▁concentration ▁of ▁car rier - based ▁aircraft ▁in ▁the ▁world ▁at ▁the ▁time . ▁Military ▁historian ▁Gordon ▁P range ▁called ▁it ▁" a ▁revolution ary ▁and ▁potentially ▁form id able ▁instrument ▁of ▁sea ▁power ." ▁ ▁Fif