: 2 0 ▁and ▁ 1 7 : 4 0 , ▁from ▁points ▁ ▁outside ▁Sydney ▁Har bour . ▁The ▁first ▁m idget ▁was ▁to ▁pass ▁through ▁the ▁He ads ▁just ▁after ▁ 1 8 : 3 0 , ▁but ▁heavy ▁se as ▁delayed ▁her ▁by ▁over ▁an ▁hour . ▁The ▁other ▁two ▁m idget s ▁followed ▁at ▁twenty - min ute ▁intervals ▁and ▁were ▁similarly ▁delayed . ▁ ▁The ▁choice ▁of ▁targets ▁was ▁left ▁up ▁to ▁the ▁m idget ▁command ers , ▁with ▁advice ▁that ▁they ▁should ▁primarily ▁target ▁aircraft ▁carri ers ▁or ▁batt les hips , ▁with ▁cru is ers ▁as ▁secondary ▁targets . ▁The ▁m idget s ▁were ▁to ▁operate ▁to ▁the ▁east ▁of ▁the ▁Har bour ▁Bridge , ▁although ▁if ▁no ▁suitable ▁targets ▁were ▁to ▁be ▁found ▁in ▁this ▁area ▁they ▁were ▁to ▁move ▁under ▁the ▁Bridge ▁and ▁attack ▁a ▁batt les hip ▁and ▁large ▁cru iser ▁believed ▁to ▁be ▁in ▁the ▁inner ▁har bour . ▁When ▁the ▁second ▁reconna issance ▁fly over ▁revealed ▁that ▁the ▁expected ▁British ▁batt les hip — — was ▁now here ▁to ▁be ▁found , ▁USS ▁Chicago ▁became ▁the ▁priority ▁target . ▁ ▁After ▁comple ting ▁their ▁mission , ▁the ▁m idget s ▁were ▁to ▁depart ▁Sydney ▁Har bour ▁and ▁head ▁south ▁for ▁ ▁to ▁the ▁recovery ▁point ▁off ▁Port ▁H ack ing . ▁Four ▁of ▁the ▁mother ▁sub mar ines ▁would ▁be ▁waiting ▁in ▁an ▁east – west ▁line ▁ ▁long , ▁with ▁the ▁fifth ▁waiting ▁ ▁further ▁south . ▁ ▁Att ack