12 June. The first two attacks resulted in 12 and 37 fatalities respectively, though the third attack killed no one. The attacks forced the authorities to institute changes in merchant traffic; travel north of Melbourne was restricted until a system of escorted convoys was established.I-21 was the only submarine to return to Australian waters, where she sank three ships and damaged two others during January and February 1943. During her two deployments, I-21 sank of Allied shipping, which made her the most successful Japanese submarine to operate in Australian waters. Bombardment On the morning of 8 June, I-24 and I-21 briefly bombarded Sydney and Newcastle. Just after midnight, I-24 surfaced south-south-east of Macquarie Lighthouse. The submarine's commander ordered the gun crew to target the Sydney Harbour Bridge. They fired 10 shells over a four-minute period; nine landed in the Eastern Suburbs and one landed in water. I-24 then crash dived to prevent successful retaliation by coastal artillery batteries. Only one shell detonated, and the only injuries inflicted were cuts and fractures from falling bricks or broken glass when the unexploded shells hit buildings. A United States Army Air Forces pilot, 1st Lieutenant George Cantello, based at Bankstown Airport disobeyed orders and took off to try and locate the source of the shelling, but was killed when engine failure caused his Airacobra to crash in a paddock at Hammondville. In 1988, following efforts by residents and the US Consulate in Sydney, the City of Liverpool established a memorial park, the Lt. Cantello Reserve, with a monument in his honour. At 02:15, I-21 shelled Newcastle, from north-east of Stockton Beach. She fired 34 shells over a 16-minute period, including eight star shells. The target of the attack was the BHP steelworks in the city. However, the shells landed over a large area, causing minimal damage and no fatalities: the only shell to detonate damaged a house on Parnell Place, while an unexploded shell hit a tram terminus. Fort Scratchley returned fire, the only time an Australian land fortification has fired on an enemy warship during wartime, but the submarine escaped unscathed. Analysis The attack on Sydney Harbour ended in failure on both sides, and revealed flaws in both the Allied defences and the Japanese tactics. During the primary attack, the Japanese lost all three midget submarines in exchange for the sinking of a single barracks ship. The subsequent operations were no more