▁ 1 st ▁Air ▁Fle et ▁was ▁a ▁land - based ▁fleet ▁of ▁" k ichi ▁k ō k ū ta i " ▁( base ▁air ▁unit ( s )). ▁ ▁Orig ins ▁ ▁In ▁ 1 9 1 2 , ▁the ▁British ▁Royal ▁Navy ▁had ▁established ▁its ▁own ▁flying ▁branch , ▁the ▁Royal ▁Naval ▁Air ▁Service ▁( R N AS ). ▁The ▁I J N ▁was ▁mode led ▁on ▁the ▁Royal ▁Navy ▁and ▁the ▁I J N ▁Admir alty ▁sought ▁establishment ▁of ▁their ▁own ▁Naval ▁Air ▁Service . ▁The ▁I J N ▁had ▁also ▁observed ▁technical ▁develop ments ▁in ▁other ▁countries ▁and ▁saw ▁military ▁potential ▁of ▁the ▁air plane . ▁In ▁ 1 9 1 3 , ▁the ▁I J N ▁se ap lane ▁car rier ▁W ak ami ya ▁was ▁converted ▁into ▁a ▁se ap lane ▁tender ▁and ▁aircraft ▁were ▁purchased . ▁The ▁ 1 st ▁and ▁ 2 nd ▁Air ▁Fle et ▁were ▁to ▁be ▁the ▁primary ▁attack ▁force ▁of ▁the ▁I J N AS . ▁ ▁The ▁Japanese ▁carri ers ' ▁experiences ▁off ▁China ▁had ▁helped ▁further ▁develop ▁the ▁I J N ' s ▁car rier ▁doctrine . ▁One ▁less on ▁learned ▁in ▁China ▁was ▁the ▁importance ▁of ▁concentration ▁and ▁mass ▁in ▁project ing ▁naval ▁air ▁power ▁ash ore . ▁Therefore , ▁in ▁April ▁ 1 9 4 1 ▁the ▁I J N ▁formed ▁the ▁ 1 st ▁Air ▁Fle et ▁to ▁combine ▁all ▁of ▁its ▁fleet ▁carri ers ▁under ▁a ▁single ▁command . ▁The ▁I J N ▁centered