On 8 February 1915, the Australian government received a request from the British Government of India for aerial assistance in the campaign against the Turks in Mesopotamia. Sufficient aircrew and supporting personnel were available for only half a flight, so the unit, the AFC's first to see active service, became known as the Mesopotamian Half Flight. Petre was appointed the Half Flight's commanding officer and embarked for Basra via Bombay on 14 April, later to be joined by fellow pilots White, Merz and Lieutenant William Treloar, along with thirty-seven ground staff.