Review - "Rocks and Rifles: The Influence of Geology on Combat and Tactics during the American Civil War" by Scott Hippensteel

[ROCKS AND RIFLES: The Influence of Geology on Combat and Tactics during the American Civil War by Scott Hippensteel (Springer, 2019). Hardcover, maps, diagrams, tables, color and B&W photographs, footnotes, references, reading lists, index. Pages main/total:x,313/331. ISBN:978-3-030-00876-5. $109.99]

The growth of interdisciplinary studies has been one of the more refreshing developments in Civil War scholarship over the past few decades. For example, the intersection of conflict archaeology and traditional Civil War documentary research has yielded an abundance of fascinating and frequently eye-opening articles and books. More confined to the domain of specialist journals has been the investigation of how geology created tactically significant topographical features of all kinds and shaped how particular Civil War battles were fought. Synthesis and interpretation of much of this work on numerous battlefields can be found in geologist Scott Hippensteel's new book Rocks and Rifles: The Influence of Geology on Combat and Tactics during the American Civil War. Beginning with the fundamental truth that the diverse landscapes upon which Civil War battles were fought were products of varying geological processes and differential weathering (both physical and chemical) that occurred over eons of time, the book explores how this geology specifically influenced the course and conduct of a select group of battles. By contrasting major differences in rock types underlying numerous Civil War battlefields, the book also attempts to show how such formations helped shape warfare at multiple scales—strategic, operational, and tactical.

Hippensteel's study begins with a brief introduction to the geological history of the eastern United States that provides readers with some helpful basic 'rules' regarding what kinds of surface terrain features are the typical result of the weathering of particular rock types and sub-types. The author also defines the five geological "provinces" (Appalachian Plateau, Valley and Ridge, Blue Ridge, Piedmont, and Coastal Plain) that make up the continental landscape east of the SW-NE running Appalachian mountain range and summarizes some general effects the major characteristics of each province had on military operations. For example, Piedmont geology generally offered both armies rolling and/or undulating ground well suited for fighting large, open battles with constraints to mass movements provided mostly by rivers. In terms of judging terrain by how well it aided defense, Piedmont geology regularly produced highly defensible ridges (the result of igneous rock intrusions) for Civil War armies to exploit as well as large expanses of ground containing deep, loose (but still adhesive) soils excellent for rapid earthwork construction.

Though most Civil War battlefields were underlain by more than one type of rock, Hippensteel organizes his largely self-contained discussions of eastern and western theater battles (ten chapters in total) around the most consequential of the earth's three basic rock categories: igneous (Second Manassas, Gettysburg), metamorphic (South Mountain, Spotsylvania Court House, Kennesaw Mountain) and sedimentary (Antietam, Fredericksburg, Stones River, Petersburg, Morris Island). Within each chapter is a strategic-level background overview and operational and tactical summaries of the battle under consideration. These sections are accompanied by a natural history of the geology of the battlefield and surrounding area along with a more focused examination of those tactical aspects of the battle most affected by geology. In discussing "tactical" influences in the book the author is not referring to particular small unit or formation-level innovations designed to overcome or exploit specific geological features but rather the tactical-scale effects of the terrain geology. For the purposes of the review, the following three paragraphs will discuss one battle from each rock grouping. This should be sufficient to provide potential readers with a sense of the kind of interpretation and analysis present in the book.

While the Union error of not securing the Thoroughfare Gap passage cut through the metamorphic quartzite ridges that surrounded it greatly aided the Confederate victory at Second Manassas, it was the igneous rock diabase ridge occupied by Stonewall Jackson's Corps that provided the tactical focal point of the battle. The long strip of rocky high ground allowed Jackson's men to withstand wave after wave of Union assaults, but geology also provided opportunity to the attackers. The two most dangerous threats to Jackson's line achieved by the Federals illustrate well a common truth that points of contact between different rock types often formed the most vulnerable areas of any defensive position. In this case, two stretches of lower ground existed along the unfinished railroad grade where the erosion-resistant igneous diabase gave way to the softer sedimentary deposits that formed the eastern part of the battlefield. The fighting at Second Manassas also produced the war's best and most vivid example of the tactical use of geology at the level of the individual, when Confederate soldiers threw large rocks at the Union attackers after their ammunition was exhausted.

The Spotsylvania battlefield sits atop "a confusing mess of ancient metamorphic and igneous rocks, fractured and folded to the point where their age and origin remain incompletely understood." (pg. 120). On the strategic and operational levels of the Overland Campaign, the more logistically friendly coastal plain meant that Grant would always favor bypassing the enemy's eastern flank, though he would still have to contend with the disadvantageous directional flow of the region's rivers. On a tactical level, Spotsylvania had two salient geological features that greatly affected how the battle was fought. The differential weathering of the metamorphic rock atop which sat Laurel Hill created a natural defensive position that was critical to repelling Union attacks there. Also, the metamorphic and igneo-metamorphic rocks in the area weathered to produced soils ideal for digging trenches and maintaining them without extensive revetment. This geology was essential to the survival of Lee's army when the collapse of the Mule Shoe salient necessitated a rapid in-battle creation of a new defensive line across its base. On the other side, the contact point between two rock formations produced a swale that allowed Union forces (on both May 10 and 12) to successfully cross open ground to attack the famous salient, the creation of which was itself influenced by the need to occupy higher ground produced by the same effects of two rock units coming together.

Finally, any serious visitor to the Stones River battlefield is unlikely to forget the natural trenches created by the sedimentary limestone karrens formed there and used by Union general Philip Sheridan's division to repulse repeated assaults on December 31. Though only a meter deep the rock formation effectively shielded Sheridan's infantry, whose sustained occupation of the sector significantly disrupted the enemy attack. Less visible limestone outcrops also affected other parts of the battlefield, either by making entrenchment impossible for defenders or by creating isolated tactically-significant plots of land like the Round Forest. The latter could not be easily cleared for either agriculture or pasturage and thus were left rugged and timbered, making them difficult ground to attack.

Complaints primarily revolve around the volume's editing problems. The book is riddled with typos and more ruthless editing might also have effectively reduced some of the more unnecessary content repetition. Fortunately, these distractions are largely offset by more positive aspects of the book's overall presentation, which includes a rather extraordinary collection of supplementary features. The book's pages fairly burst with photographs (b&w and color), maps, tables, charts, and diagrams, all usefully connected to the text.

If you're like most readers with little geology knowledge beyond middle school earth science and the three basic rock categories (igneous, metamorphic, and sedimentary), the nomenclature presented in the book can be a bit daunting in places. However, the background help is far from unforgiving and astute readers lacking an advanced grounding in geology should have little problem absorbing a reasonable understanding of the main concepts through context and occasional search engine assistance.

Authors are, of course, free to pursue their own interests, but it deserves mention that the book's limited geographical spread only tells part of the geological story of the Civil War. Several prominent examples of visible geology affecting Trans-Mississippi campaigns and battles spring to mind. The bluffs, rock ridges, and deep hollows intersecting the Pea Ridge battlefield in Arkansas to a great degree shaped the course of that battle and the geological legacy of the New Madrid Fault Line certainly influenced General John Pope's Island No. 10 campaign.

Overall, Scott Hippensteel's Rocks and Rifles succeeds admirably in bringing a renewed appreciation of geology to Civil War military history. It is certainly true that intimate knowledge of the ground is an essential prerequisite for comprehensive mastery of any given battle history, and Hippensteel's study offers readers and experts alike a series of fresh and informed glimpses of yet another layer of understanding.