Slave raiding is a military raid for the purpose of capturing people and bringing them from the raid area to serve as slaves. Once seen as a normal part of warfare, it is nowadays widely considered a crime. Slave raiding has occurred since antiquity. Some of the earliest surviving written records of slave raiding come from Sumer (in present-day Iraq). Kidnapping and prisoners of war was the most common source of African slaves, although indentured servitude or punishment also resulted in slavery.