Island group, western Pacific Ocean.
Lying northwest of New Guinea , it forms part of Papua New Guinea . It has a total area of 19,173 sq mi (49,658 sq km); its largest components include New Britain , New Ireland , the Admiralty Islands , and New Hanover (Lavongai). Annexed by Germany in 1884, it was named for Otto von Bismarck . Occupied by Australia in 1914, it was made a mandated territory of Australia in 1920. The group became part of the UN Trust Territory of New Guinea after World War II and part of Papua New Guinea when it attained independence in 1975.