 During World War II the coastal artillery defences of Moreton Bay were upgraded.These included Fort Lytton (1880-1881) (now Fort Lytton National Park) on the southern side of the Brisbane River's mouth and Fort Cowan Cowan (late 1930s) (Fort Cowan Cowan), on the west side of Moreton Island.Fort Bribie (Bribie Island Second World War Fortifications), at the northeast tip of Bribie Island, was established in 1939 after Germany's invasion of Poland plunged the world into war.