Why Indonesia stretches so far

An eighth of the way round the world

Indonesia lies across the Equator between the Indian and Pacific oceans, and its islands span a distance equal to one-eighth of the Earth’s circumference: about 5,100 km from east to west and 1,800 km from north to south. There are some 17,500 of them, more than 7,000 uninhabited.^[1]

They sit where major pieces of the Earth’s crust meet. Borneo and the arc of Sumatra, Java, Bali and the Lesser Sundas rise from the Sunda Shelf, an extension of the Asian continent, while New Guinea sits on the Sahul Shelf.^[1]

The shape of a colony

Indonesia was formerly the Dutch East Indies.^[1] Much of it came under Dutch control only between 1870 and 1910: a war with Aceh that lasted, on and off, from 1873 to 1908 brought northern Sumatra under Dutch control, and treaties with local rulers extended Dutch authority over Celebes, central Borneo, Bali, the Lesser Sundas and the Moluccas, with footholds in western New Guinea. In doing so, Britannica says, the Dutch laid the foundations of the future Indonesian republic.^[3]

Indonesia declared independence in 1945, and the Netherlands recognised its sovereignty in 1949.^[1] The Dutch kept western New Guinea, which Indonesia campaigned to recover; only when the UN acknowledged it as part of Indonesia in 1969 did the country take its present form.^[4][1] Indonesia also took over East Timor, a former Portuguese territory, in 1976, but after a UN-organised referendum in 1999 it became independent, fully sovereign from 2002.^[1]

Seas that join instead of divide

Under the old rules, the waters between Indonesia’s islands counted as open ocean that belonged to no one, which left the country, in the Jakarta Post’s words, “made up of pieces of territory separated by international seas”. On 13 December 1957 Prime Minister Djuanda Kartawidjaja declared that those waters belonged to Indonesia, joining its islands and seas into a single territory.^[2]

The idea was written into the 1982 UN Convention on the Law of the Sea.^[2] It defines an archipelagic state, lets one draw straight baselines joining its outermost islands, each normally no longer than 100 nautical miles, and gives it sovereignty over the waters inside them.^[5]

“The sovereignty of an archipelagic State extends to the waters enclosed by the archipelagic baselines”^[5]