?Chapter 1 surveys the types of brigades and divisions the Army employed in the various wars of the 18th and 19th centuries.  These units and the doctrine underlying them were the basis for organizing and maintaining permanent divisions and brigates in the 20th century.  Chapters 2 through 14 trace the evolution of the United States Army divisions and separate brigades from approximately 1900 to 1990.  Their various reorganizations and their roles in the total Army are the grist of the study.  Chapter 15 draws together some of the lessons explored in the main body of the volume.  Since the manuscript was prepared seven years ago momentous changes have occurred in the Army, and a brief look forward examines some of them.