▁large ▁Japanese ▁sub mar ines ▁s ank ▁only ▁three ▁merchant ▁ships ▁and ▁caused ▁minimal ▁property ▁damage ▁during ▁the ▁two ▁bomb ard ments . ▁The ▁performance ▁of ▁the ▁Al lied ▁def enders ▁was ▁equally ▁poor . ▁However , ▁one ▁historian ▁states ▁that ▁the ▁lack ▁of ▁damage ▁in ▁Sydney ▁Har bour ▁was ▁due ▁to ▁" a ▁combination ▁of ▁good ▁luck ▁and ▁ag gress ive ▁counter - att ack ". ▁ ▁The ▁main ▁impact ▁of ▁the ▁m idget ▁sub marine ▁attack ▁and ▁subsequent ▁operations ▁was ▁psych ological ; ▁disp elling ▁any ▁belief ▁that ▁Sydney ▁was ▁imm une ▁to ▁Japanese ▁attack ▁and ▁highlight ing ▁Australia ' s ▁proxim ity ▁to ▁the ▁Pacific ▁War . ▁There ▁was ▁no ▁official ▁inqu iry ▁into ▁the ▁attacks , ▁despite ▁demand ▁from ▁some ▁sections ▁of ▁the ▁media , ▁as ▁there ▁was ▁concern ▁that ▁an ▁inqu iry ▁would ▁lead ▁to ▁defeat ism ▁and ▁reduce ▁faith ▁in ▁John ▁Curt in ' s ▁government , ▁particularly ▁after ▁the ▁dam aging ▁inqu iry ▁into ▁Australian ▁def ences ▁that ▁had ▁followed ▁the ▁Japanese ▁aer ial ▁attack ▁on ▁Dar win ▁three ▁months ▁earlier . ▁ ▁Fail ures ▁in ▁Al lied ▁def ences ▁The ▁Al lies ▁failed ▁to ▁respond ▁ade qu ately ▁to ▁several ▁warnings ▁of ▁Japanese ▁activity ▁off ▁the ▁east ▁coast ▁of ▁Australia ▁prior ▁to ▁the ▁attack ; ▁they ▁simply ▁ignored ▁the ▁warnings ▁or ▁explained ▁them ▁away . ▁They ▁attributed ▁the ▁un success ful ▁attack ▁on ▁the ▁fre ighter ▁W ellen ▁on ▁ 1 6 ▁May ▁to ▁a ▁single ▁sub marine , ▁and ▁assumed ▁it ▁had ▁depart ed