In Australia, Casey became Chief Engineer at MacArthur's General Headquarters (GHQ), Southwest Pacific Area (SWPA). He faced enormous engineering challenges. Most of New Guinea consisted of mountains and jungle, with very few airstrips, ports or roads. All of these had to be developed to support operations. To provide additional expertise in construction, Casey had Leif Sverdrup assigned to his staff as chief of the Construction Section, with the rank of colonel. As U.S. Army engineers were few, Casey worked closely with his Australian Army counterpart at General Sir Thomas Blamey's Allied Land Forces headquarters, Major General Clive Steele. Construction activities in Australia were also undertaken by civilians of the Allied Works Council. Casey attempted to coordinate the activities of the various agencies. He had to fend off attempts by the U.S. Army Air Forces to gain control of his aviation engineer battalions. The Royal Australian Air Force organized its own airbase construction squadrons and only with difficulty was Casey able to control their activities.