When the American Civil War began in 1861, people on both sides of the conflict believed that the conduct of soldiers and civilians would shape if not determine the war's outcome. In this context, the nation-wide temperance movement began a period of transition. Before the 1860s, interest in temperance was waning nationally; local and state regulatory measures had curbed excessive drinking. Once war broke out, however, alcohol became increasingly threatening. Soldiers and officers drank heavily, lacked discipline, and harassed civilians. Distillers and traffickers wasted grain and profited during a time of scarcity, when most civilians practiced patriotic self-sacrifice. Temperance reformers believed that ridding the nation - either the Union or the Confederacy - of alcohol was the only way to curb immorality, whip the armies into fighting shape, and win the war. Many Americans outside of the temperance movement agreed. Debates over alcohol's manufacture and consumption became essential components for understanding what it meant to be a patriotic citizen during the Civil War. In turn, examining these wartime issues recasts historical understandings of the centrality of temperance to conceptions of nationalism in the post-bellum United States. This study relies on a variety of sources: military records, legislative journals, temperance and religious publications, personal accounts, and newspapers. It examines soldiers' uses and beliefs about drinking; the supply of alcohol in the armies; regulatory debates on the northern and southern home fronts; and northern and southern temperance reformers' understandings of the war's purposes. It argues that when it came to alcohol northern and southern civilians clashed with military officials. Union and Confederate military officials knew that whiskey was responsible for chronic indiscipline, but they nevertheless supplied alcohol to soldiers to stave off illness and fatigue. Soldiers drank willingly. Alcohol took the edge off the war. On the home front, however, civilians regarded liquor as an enemy in its own right. Temperance reformers implored soldiers to put down the bottle. Union and Confederate civilians demanded that military and civil authorities prohibit distilling to restore order and preserve food. In doing so, they laid the foundations for the post-war prohibition movement.