Headhunting has been practiced across the Americas, Europe, Asia, and Oceania for millennia.[4] One analysis of the practice in early North American societies linked it to social distance from the victim.[5] Groups such as the Scythians collected the skulls of the vanquished to make a skull cup.[citation needed] The practice continued up until the 20th century in the Balkans, and occurred on a smaller scale during World War II and the Vietnam War.