Artillery played an important and perhaps decisive role in the July 1863 battle of Gettysburg. Although many hundreds of books have been published on the battle, very few have focused more than a few paragraphs or a sprinkling of entries on the "long arm" and its role in the battle. This gap is finally filled by George Newton's Silent Sentinels: A Reference Guide to the Artillery of Gettysburg. Now in paperback, Newton's well-written and illustrated study was designed to be of use to both the casual battlefield visitor and the serious Civil War scholar. The former will use Silent Sentinels to learn more about the campaign in general, the role of artillery in Civil War battles, and how it was used on the battlefield at Gettysburg. They will also use it to learn how to identify different types of artillery, and tour a wide variety of artillery-related sites from Oak Hill in the north to a solitary gun well south of the Peach Orchard. More experienced Civil War students will find Silent Sentinels' extensive primary sources, diagrams, appendices of numbers and losses, and informative discussion of artillery organization and tactics an indispensable reference resource. Silent Sentinels opens with a general overview of the campaign and a wide-ranging discussion of 19th century artillery, the gun types used at Gettysburg, the equipment needed to operate the guns, how they were organized in each army, and the tactics employed by both Union and Confederate artillerymen. The chapter-long and wide-ranging tour included in this book guides readers to a variety of fascinating sites with enough detail to interest even the most jaded Gettysburg historian. This outstanding and useful historical guide includes detailed endnotes, a bibliography, and an index. Readers can peruse and enjoy this versatile study from the comfort of an easy chair or while walking the magnificent Pennsylvania field.