Batak warriors in 1870. The term "Batak" is used to collectively identify a number of ethnic groups predominantly found in North Sumatra, Indonesia. It includes the Toba, Karo, Pakpak, Simalungun, Angkola and Mandailing, each of which are distinct but related groups with distinct, albeit related, languages and customs (adat).Photo: Kristen Feilberg; Restoration: Peter Weis