Gun rights advocates claim the case as a victory because they interpret it as stating that ownership of weapons for efficiency or the preservation of a well-regulated militia unit is specifically protected. Furthermore, they frequently point out that short-barreled shotguns (with 20-inch barrels) have been commonly used in warfare and that the statement made by the judges indicates that they were not made aware of this fact. Because the defense did not appear, there was arguably no way for judges to know otherwise. Two of the justices involved in the decision had prior military experience, Justice Black as a captain in the field artillery during World War I and Justice Frankfurter as a major in the Army legal service; however, there is no way to know if they were personally aware of the use of shotguns by American troops. During World War I, between 30,000 and 40,000 short-barreled pump-action shotguns were purchased by the US Ordnance Department and saw service in the trenches and for guarding German prisoners.