Dutch East Indies campaign
The Dutch East Indies campaign of 1941–1942 was the conquest of the Dutch East Indies (present-day Indonesia) by forces of the Empire of Japan in the early days of the Pacific campaign of World War II. Allied forces attempted unsuccessfully to defend the islands. The East Indies were targeted by the Japanese for their rich oil resources which would become a vital asset during the war.
Source: Wikipedia — Dutch East Indies campaign (CC BY-SA 4.0)