Zachery Fry’s study of political culture within the Army of the Potomac sheds new light on old questions. It builds on a robust body of scholarship that explores how American soldiers brought their politics into the United States military, and how their time in uniform transformed their political worldview. Focusing on the “common soldier,” works by James McPherson, Chandra Manning, Earl Hess, Gary Gallagher, Peter Carmichael, and Jonathan White (among many others) have probed why they enlisted, how they understood race, slavery, emancipation, and Union, how they voted, and how their experiences changed them. What distinguishes Fry’s new work is his focus on junior officers in the Army of the Potomac, an intriguing subset of the military that has been largely neglected by historians. As a group, junior officers tended to be older, better educated, and more politically engaged than enlisted men. Fry argues that they formed a “distinct political culture” (10). According to Fry, these junior officers began the war as active political partisans and only became more politically committed as the war progressed. In 1861, the ranks of the junior officer corps were already deeply divided along partisan lines. The disastrous Peninsula Campaign of 1862 prompted many of them to turn against General George McClellan and, by extension, the Democratic Party. While many junior officers expressed reservations about Abraham Lincoln’s Emancipation Proclamation, they rejected Democratic efforts to undermine administration policies as unpatriotic. Early in the war, many Democratic state legislatures prohibited soldiers’ voting, citing technicalities to restrict their suffrage. Although disenfranchised, junior officers remained politically active and engaged, contributing to newspapers and writing impassioned letters home. In fits and starts, they became increasingly devoted to supporting the Lincoln administration and the Republican Party. In the epilogue, Fry traces how wartime political activism shaped the postwar lives of Union veterans.