The US Army infantry division was an intricate system of men and equipment welded together by doctrine and organization into an entity that could fight, maneuver, communicate within itself as well as with outside entities, and regenerate itself through a supply and replacement system. This book examines the organizational development, mobilization, deployment and combat actions of World War II US Army infantry divisions up until the end of 1943. Among the units covered are the separate infantry regiments and battalions of the "standard" type, showing how the Army's new "triangular" infantry division (based on three infantry regiments) evolved from the earlier "square" division (based on four).

John J Sayen Jr retired in August 2003 from 30 years active and reserve service with the United States Marine Corps. During that time he served with artillery, armour and military intelligence. He is presently engaged as a contract civilian analyst for the Marine Corps. He graduated from the Citadel in 1974. He has published a military-historical magazine, 'The Tactical Notebook'. This is his first book for Osprey. He lives in Virginia, USA.