The Royal Netherlands East Indies Army (Dutch: Koninklijk Nederlands Indisch Leger; KNIL, Dutch pronunciation: [knl]) was the military force maintained by the Kingdom of the Netherlands in its colony of the Dutch East Indies, in areas that are now part of Indonesia. The KNIL's air arm was the Royal Netherlands East Indies Army Air Force. Elements of the Royal Netherlands Navy were also stationed in the Netherlands East Indies.

The Aceh War (Indonesian: Perang Aceh), also known as the Dutch War or the Infidel War (1873–1904), was an armed military conflict between the Sultanate of Aceh and the Kingdom of the Netherlands which was triggered by discussions between representatives of Aceh and the United States in Singapore during early 1873. The war was part of a series of conflicts in the late 19th century that consolidated Dutch rule over modern-day Indonesia.

The campaign drew controversy in the Netherlands as photographs and accounts of the death toll were reported. Isolated bloody insurgencies continued as late as 1914 and less violent forms of Acehnese resistance continued to persist until World War II and the Japanese occupation.