In the early 18th century, the Pawnee numbered more than 60,000 people. They lived along the Loup (ickariʾ) and Platte (kíckatuus) river areas for centuries; however, several tribes from the Great Lakes began moving onto the Great Plains and encroaching on Pawnee territory, including the Dakota, Lakota (páhriksukat / paahíksukat) ("cut throat / cuts the throat"), and Cheyenne (sáhe / sáhi). The Arapaho (sáriʾitihka) ("dog eater") also moved into Pawnee territory. Collectively, the Pawnee referred to these tribes as "cárarat" ("enemy tribe") or "cahriksuupiíruʾ" ("enemy"). The Pawnee were occasionally at war with the Comanche (raaríhtaʾ) and Kiowa (káʾiwa) farther south. They had suffered many losses due to Eurasian infectious diseases brought by the expanding Europeans and European-Americans. By 1860, the Pawnee population was reduced to 4,000. It further decreased, because of disease, crop failure, and warfare, to approximately 2,400 by 1873, after which time the Pawnee were forced to move to Indian Territory, which later became Oklahoma. Many Pawnee warriors enlisted to serve as Indian scouts in the US Army to track and fight their tribal enemies resisting American expansion on the Great Plains.