During the fighting for Rabaul in early 1942, No. 24 Squadron RAAF fought a brief, but ultimately futile defence as the Japanese advanced south towards Australia. The devastating air raids on Darwin on 19 February 1942 increased concerns about the direct threat facing Australia. In response, some RAAF squadrons were transferred from the northern hemisphere—although a substantial number remained there until the end of the war. Shortages of fighter and ground attack planes led to the acquisition of US-built Curtiss P-40 Kittyhawks and the rapid design and manufacture of the first Australian fighter, the CAC Boomerang. RAAF Kittyhawks came to play a crucial role in the New Guinea and Solomon Islands campaigns, especially in operations like the Battle of Milne Bay. As a response to a possible Japanese chemical warfare threat the RAAF imported hundreds of thousands of chemical weapons into Australia.