From Wikipedia
Hardtack was the first U.S. published American Civil War rules set and had an early following. However, by the end of the decade, it had been supplanted by Scott Bowden's Stars and Bars and John Hill's Johnny Reb 3 and is rarely played at modern wargaming conventions. However, it is considered as groundbreaking, and ushered an era of Civil War miniature wargaming in the USA.
Introduction by Gary Gygax
Painting Guide by Don Lowry
Guidon Games Product # WM103
Preface:
This comprehensive set of rules is designed to take a person who has never played miniatures before thru several increasing stages of realism to the point where he can create for himself the kind of Civil War game which is most suited to his own personality. When you have read and played everything this booklet contains, you will be prepared to design a Civil War game which has all the simplicity necessary for a great game. The first version described is called the TRAINING GAME because it is designed to teach the basic mechanics of recreating Civil War battles with miniatures soldiers. When it can be played without referring back to the rules, learn the more realistic BASIC GAME.