The Aceh War, (1873-1904), an armed conflict between the Dutch and the sultanate of Muslim Aceh (also spelled Acheh, or Aceh) in northern Sumatra which resulted in Dutch conquest of the Acehnese and, ultimately, in Dutch control of the whole region. In 1871 the Netherlands and Britain signed an agreement recognizing the influence of the Dutch in northern Sumatra in return for Dutch confirmation of Britain's equal trade rights in the East Indies.
The Dutch, considered Aceh as their territory of influence, decided to conquer the area and sent two expeditions to Aceh in 1873. The palace was captured and soon the Aceh sultan died. The Dutch stopped military operations and made agreements with the new sultan, who recognized Dutch sovereignty over the region. However, he was unable to control his people, and Dutch forces were involved in prolonged guerrilla warfare in the countryside. But this war drained the colonial treasury, and public opinion in the Netherlands became increasingly critical of the colonial administration.
The government then realized that their ignorance of the area had caused them to make serious mistakes. Christiaan Snouck Hurgronje, professor of Islamic studies at Leyden University (Leiden), was invited to conduct a thorough study of Aceh and publish a book in 1893-1984 about Acehnese. "Strategy of the castle," which provided fortified bases for Dutch troops, then was introduced. Under the leadership of J.B. van Heutsz, who was appointed Acehnese military and civil governor in 1899, the kingdom was quickly subdued. Conquest of the entire region was carried out by van Heutsz in 1904.
When did the Netherlands and Britain sign the agreement about the influence of the Dutch in Sumatra?