The Achinese War [also Aceh War] (1873-1904) was one of the longest and bloodiest in Dutch-Indonesian history. This armed conflict between The Netherlands and the Muslim sultanate of Acheh [now Aceh] in northern Sumatra resulted in Dutch conquest of the Achinese and, ultimately, in Dutch domination of the entire region. An estimated 4000 Dutch and 25,000 Achinese died in the fighting.
The 1824 Treaty of London defined a British sphere of influence on the Malay Peninsula and a Dutch sphere on Sumatra, although its provisions placed no restrictions on British trade on the island. Sumatran trade became an issue of contention, however, because the British resented what they saw as Dutch attempts to curtail their commercial activities. One provision of the Treaty of London was the independence of the north Sumatran state of Acheh. But Acheh controlled a large portion of the pepper trade and alarmed the Dutch by actively seeking relations with other Western countries. A new Anglo-Dutch treaty, signed in 1871, gave the Dutch a free hand in Sumatra concerning Acheh in return for Dutch confirmation of Britain's right of equal trade in the Indies. Two years later, talks between the United States consul in Singapore and Achinese [also Acehnese] representatives gave Batavia the pretext for opening hostilities.
The Dutch, considering Acheh as within their sphere of influence, decided to conquer the area and sent two expeditions to Acheh in 1873. Dutch gunboats bombarded the sultanate's capital, Banda Acheh, and troops were landed. The palace was seized and shortly afterward the Achinese sultan died. The Dutch suspended military operations and concluded a treaty with the new sultan, who recognized Dutch sovereignty over the area. He was unable to control his subjects, however, and Dutch forces became involved in a prolonged guerrilla war in the countryside. This war, however, drained the colonial treasury, and public opinion in The Netherlands became increasingly critical of the colonial administration.
The administration later realized that their ignorance of the region had led them to commit serious errors. C. Snouck Hurgronje, professor of Islamic studies at the University of Leyden, was invited to undertake a thorough study of Acheh and published a book in 1893-94 on the Achinese. A "castle strategy," which provided fortified bases for the Dutch troops, was then introduced. Under the leadership of J.B. van Heutsz, who was appointed military and civil governor of Acheh in 1899, the kingdom was quickly subdued. The conquest of the entire region was accomplished by van Heutsz in 1904.