[The Army of the Potomac: Order of Battle, 1861-1865, with Commanders, Strengths, Losses and More by Darrell L. Collins (McFarland (800-253-2187), 2013). Softcover, OBs, notes, bibliography, index. 334 pp. ISBN:9780786473465 $75]
Like the typical order of battle one finds in Civil War campaign histories, Collins arranges the entire army unit and command structure in cascading fashion: army --> corps (if applicable) --> division --> brigade --> individual regiments and batteries. The officer in charge of each unit, as well his casualty status and replacement, is named when the information is available. The muster in date for all the regiments is provided, as are casualty numbers broken down into killed, wounded, and missing; loss totals; and percentage lost when numbers present are known. At the end of each order of battle is a number and loss summary at division or corps scales, and a list of the ten regiments with the highest casualties suffered over the course of the battle or campaign. The information is all organized in an easy to read and comprehend tabular format.
The sole source used to create the orders of battle is the Official Records, with use of Dyer's Compendium for muster-in dates and Heitman's Historical Register for officer first names. Across the board consistency presumably has something to do with this choice, but the author's own explanation for limiting his sources is that all figures represent estimates and the modern reexaminations and reformulations have controversies of their own on some level. It is true that the OR OBs have generally stood the test of time, and the majority of battle and campaign history authors simply copy them into their works with little or no critical contribution of their own, but there are errors and omissions in the OR and it is unfortunate that so many blank spaces in Collins's compilation exist when well researched and well respected references are available to fill them [for instance, the Gettysburg battle has more than one exhaustive number and loss study in print]. Given the content claims of the book's subtitle, many readers will be disappointed to find so few strength figures, especially at the regimental level. Present for duty numbers are consistently available only at brigade level and above. This scarcity of data is in contrast with artillery battery compositions, which all have numbers of guns and tube types listed (there is even occasional trivia added like 'total rounds fired'). But even this seemingly more thorough OB representation has problems of identification. For instance, Collins lists the 12-pounders present in batteries without differentiating between the 12-lb howitzer and the Napoleon. It is true the Union army, especially in the East, retired the outdated howitzers from their field batteries quicker and more thoroughly than their Confederate counterparts, but it would have been helpful to have definitive IDs.
While readers expecting exhaustively researched and fully articulated orders of battle for the Army of the Potomac will be disappointed in varying degrees with Collins's limited work, the author deserves real credit for completing the thankless task that no one else has been willing to perform before now, that of compiling the OB lists and data available in the OR and gathering them all together in one place for easily accessible viewing. The basic information provided will answer the purposes of most readers and the baseline data is serviceable as a valuable starting point for more intensive research