Arther Ferrill (born 1938),[1] now a professor emeritus of history at the University of Washington at Seattle,[2] is a respected expert on ancient Rome and military history.
[1] He went on to graduate study at the University of Illinois at Urbana-Champaign, where he received a master's degree in 1961 and a Ph.D. in 1964.
[1] In The Fall of the Roman Empire: The Military Explanation (1998 ISBN 0-500-27495-9), Ferrill supports the claims of Vegetius, about increased "barbarisation" and "germanisation" helping to cause the collapse of the Western Roman Empire in the fifth century AD.
He asserts that allowing barbarians to settle within Rome's borders, to act as a buffer zone against other barbarians, created friction and led to a decrease in the size of the Roman Empire's Borders.
For example, field army units would not use their helmets, the pilum was replaced, and the standard of drill declined, leading to a lack of military skill within the empire.