From a story at War History Online:
The Battle of Darwin was the single largest attack on Australian soil during WWII. A group of 242 Japanese aircraft bombed the small town in which a strategically important Allied base and harbor were located... When he was found, after the attack, [Gunner, a six-month-old shepherd dog] had a broken leg...It only took a few weeks for him to demonstrate his skills. One day, while the airport at Darwin was being reconstructed, Gunner became agitated, jumping about, barking and whining. Soon after, the sound of aircraft engines was heard, while a Japanese attack formation once again flooded the sky above Darwin... The airmen of Darwin connected the dots and realized a pattern between Gunner’s shift of behavior and the bombing raid. The next time the Japanese decided to attack Darwin, their luck had run out. More than 20 minutes before their arrival, Gunner had already sounded the alarm. For the first time, the Australians were ready to repel the attack...He correctly distinguished the different sound of Allied aircraft and that of the Japanese, without ever making a single mistake. His trait was taken very seriously in a time of war. Wing Commander McFarlane even issued an order by which a portable air raid siren was to be activated whenever Gunner showed his well-known signs of alert...Whether he survived the war remains unclear, for apart from the legend which grew around him, Gunner’s existence was rarely mentioned in the official military documents of the time.