"In a style that is clear, unhurried and . . . vigorous, Francis P. Prucha has written a definitive study of the] frontier army that was itself a pioneer. It pushed the line of occupation far beyond settlements. It raised crops, herded cattle, cut timber, quarried stone, built sawmills and performed the manifold duties of pioneers. It restrained lawless traders, pursued fugitives, ejected squatters, maintained order during peace negotiations and guarded...