After launching their Pacific War, the Imperial Japanese Navy managed to infiltrate New South Wales waters and in late May and early June 1942, Japanese submarines made a daring series of attacks on the cities of Sydney and Newcastle. On the night of 31 May–1 June 1942, three midget submarines were launched from their large "mother" submarines east of Sydney to enter Sydney Harbour to attack shipping located there: principally the cruisers USS "Chicago" and HMAS "Canberra".