The workhorse of the German Army that swept across Poland, France and Russia, the Sturmgeschutz I saw service in all theatres of World War I, both in an infantry support role and as a tank destroyer. Cheaper and quicker to produce than a tank, the assault gun proved a remarkably effective weapon. Its design and development, production, capabilities and operational history are all closely examined, as is its tactical employment and organisation into units. This book uses original German combat and experience reports to show how the Sturmgeschutz fared in action, whilst also providing information on both retrofitted and production modifications.