KNIL is the abbreviation for a Dutch army. This army was in what is now called Indonesia. The official name is Koninklijk Nederlandsch-Indisch Leger (Royal Dutch-East Indies Army)
Indonesia was a Dutch colony from 1800 to 1949. It was then called Nederlandsch Indië (Dutch East Indies). The KNIL taskforce was sent there to maintain order.
When Indonesia declared itself independent in 1945 the Dutch fought a war to keep the colony. This war was won by the Indonesians. The Dutch government accepted Indonesia's independence in 1949, and the KNIL ceased to exist.