 The most valuable group, in Askania Nova, Ukraine, was shot by German soldiers during World War II occupation, and the group in the United States had died out.Competition with livestock, hunting, capture of foals for zoological collections, military activities, and harsh winters recorded in 1945, 1948, and 1956 are considered to be the main causes of the decline in Przewalski's horse population.By the end of the 1950s, only 12 individual horses were left in the world.