Casey's initial need was for engineer units to accomplish the daunting construction program, but soon stocks of engineer supplies and equipment began to run low. This was exacerbated by incoming units arriving without their equipment, or with it stowed on numerous ships, which often arrived at various ports in a theater where ports were hundred or thousands of miles apart. Critical shortages developed of tractors, graders, concrete mixers and welding equipment. In the absence of a proper stock control system, an overall coordinating agency, and adequate numbers of engineer depot units, the allocation and distribution of the meager supplies on hand were difficult tasks. The worst problem was spare parts. Equipment was operated around the clock under harsh conditions and soon wore out or broke. A large proportion of equipment became unserviceable for lack of spare parts. Requisitions sent to the United States took months to arrive, so recourse was made to the limited sources of supply in Australia.