Scholars have long tried to explain why Union general George McClellan's campaign to capture Richmond, Virginia, in the summer of 1862 failed. With the exception of some limited attention to weather and terrain, Civil War historians have essentially ignored the complex natural world in which McClellan made his critical decisions. Employing methodology from both environmental and military history provides new insights into the actions of both Union and Confederate armies. The environment McClellan encountered brought out the worst in the general, magnifying the personal traits and quirks that led to some of his most baffling command decisions. Simultaneously, Confederate forces used nature to their advantage, employing strategies that allowed their armies to stave off a potentially devastating conquest of Richmond.