In July 1942, the 2nd Group of 14th Kokutai (Air Group), Japanese Naval Air-Force, under the command of Major Misaburo Koizumi, decided to undertake night raids on harbour facilities and airfields at Townsville. In all, five raids were planned; three actually occurred. After the first two raids, there was to be another attack on the night of 28 July, but this did not proceed and no details were recorded. The aircraft destined to attack Townsville on 31 July experienced difficulties and decided to bomb near Cairns instead.

Later code named by the Allies as “Emily", the Kawanishi H8K1 flying boat was an advanced design and regarded as extremely difficult to shoot down. Heavily defended, its armaments comprised dorsal and tail turrets cannons, with machine-guns in two beam blisters, ventral and cockpit hatches and bow turret. Not only did it carry considerable protective armour, its fuel tanks were partially self-sealing and designed that if punctured, fuel was collected and pumped into undamaged tanks. Additionally, the hull tanks carried a carbon-dioxide fire extinguisher system. With a range of 2567 miles, this meant that a fifteen hour flight to a target such as Townsville and returning to base was possible.