▁launch ▁due ▁to ▁technical ▁difficulties . ▁The ▁first ▁attack ▁included ▁three ▁groups ▁of ▁plan es : ▁▁ 1 st ▁Group ▁( target s : ▁batt les hips ▁and ▁aircraft ▁carri ers ) ▁▁ 4 9 ▁Nak aj ima ▁B 5 N ▁Kate ▁bom bers ▁armed ▁with ▁ 8 0 0   kg ▁( 1 7 6 0   lb ) ▁arm or - p ier cing ▁bomb s , ▁organized ▁in ▁four ▁sections ▁( 1 ▁failed ▁to ▁launch ) ▁▁ 4 0 ▁B 5 N ▁bom bers ▁armed ▁with ▁Type ▁ 9 1 ▁tor ped o es , ▁also ▁in ▁four ▁sections ▁▁ 2 nd ▁Group ▁– ▁( target s : ▁Ford ▁Island ▁and ▁Whe eler ▁Field ) ▁▁ 5 1 ▁A ichi ▁D 3 A ▁Val ▁d ive ▁bom bers ▁armed ▁with ▁ ▁general - pur pose ▁bomb s ▁( 3 ▁failed ▁to ▁launch ) ▁▁ 3 rd ▁Group ▁– ▁( target s : ▁aircraft ▁at ▁Ford ▁Island , ▁H ick am ▁Field , ▁Whe eler ▁Field , ▁Bar ber ' s ▁Point , ▁K ane o he ) ▁▁ 4 3 ▁M its ub ishi ▁A 6 M ▁" Zero " ▁f igh ters ▁for ▁air ▁control ▁and ▁st raf ing ▁( 2 ▁failed ▁to ▁launch ) ▁ ▁As ▁the ▁first ▁wave ▁approached ▁O ahu , ▁it ▁was ▁detected ▁by ▁the ▁U . S . ▁Army ▁S CR - 2 7 0 ▁rad ar ▁at ▁Op ana ▁Point ▁near ▁the ▁island ' s ▁northern ▁tip . ▁This ▁post ▁had ▁been ▁in