Mike,

Used in the military context, an Artificer is a military mechanic, i.e. one who repairs military equipment and ordinance. Artificer was more of a billet than a rank. Apparently if a man was an adept craftsman, such as a carriage maker or blacksmith he was much in demand especially in artillery units. Much as a farrier would in the cavalry. Although farrier is an occupation the U.S. Army in the old days considered it a rank status as they did the term artificer. My maternal grandmother's brother served in WW 1 in a cavalry unit in France and on his grave marker his rank is listed as Farrier. The term artificer was used in much the same context.
Len