Dennis Mahan’s Leadership and Tactics: How a West Point Professor Shaped the Course of the Civil War

By Nick Tarchis ’18

This summer, while doing research at Stratford Hall, I happened across the name of one West Point professor who quite literally taught every cadet who fought in the Civil War. It is fairly common knowledge than many of the war’s great commanders were classmates together at West Point. For example, the class of 1842 contained George McClellan, James Longstreet, and John Pope. Such commanders influenced the course of the war by drawing upon their West Point education, and while they may have held different military outlooks, they all drew upon the teachings of one man: Dennis Mahan, professor of mathematics as well as military and civil engineering. Thus, Mahan, a relatively unknown figure, had a direct impact on how the war was waged during some of its most crucial days.

Professor Mahan graduated at the top of his class at West Point in 1824 and began his teaching career almost immediately after. The U.S. government even sent him to France for a number of years to observe European tactics. While abroad, he saw how the French used forts and extensive defensive positions to protect their cities. His class on military science at West Point directly correlated onto the battlefield, one of his key points being the use of fixed fortifications and defenses in theatre. Mahan also stressed the importance of using the surrounding geography to an army’s advantage. By 1863, the war came to a head when George Meade and Robert E. Lee, both students of Mahan, clashed here at Gettysburg. From the beginning of the engagement, Mahan’s teachings were visible. For example, Lee famously used the mountains around Gettysburg to mask his movement from the Army of the Potomac. Culp’s Hill is another area where Mahan’s teachings were used, though it tends to be overshadowed by other areas of the battlefield.

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Dennis Mahan. Photo via National Park Service.

This is not to say that certain areas are more important or noteworthy than others, but much of the history of Little Round Top and Cemetery Ridge already has a large scholarly following. For example, the Second Corps’ action on July 3rd has been the focus of numerous books every year–most recently Pickett’s Charge: A New Look at Gettysburg’s Final Attack by Phillip Tucker–while many facets of the battle still remain untouched. Pickett’s Charge often takes the spotlight when it comes to discussing the third day, but a considerable part of the battle centered around Culp’s Hill and culminated in a Confederate attack at dawn on July third. On that morning, Richard Ewell’s forces clashed with the Union 12th Corps commanded by George Greene, a descendant of the famed revolutionary general Nathaniel Greene and a classmate of Dennis Mahan. Greene clearly subscribed to Mahan’s philosophy of battle, as the Confederate attack was crushed against the Union’s strong fortifications and stymied by its defensive strategy. When the Confederates attacked, they were met with entrenchments that Union soldiers dug during the fighting. The troops were able to dig thanks to Greene’s strategy of shuttling troops from Cemetery Ridge up to Culp’s Hill and using these men to stave of the repeated attacks while others dug entrenchments. It was these defensive tactics that were vital to holding to Culp’s Hill, and if Greene and his corps had failed, the Union Army’s right flank would have collapsed in on itself.

After living and working in Gettysburg for almost four years, I have come to realize that there are many stories surrounding the battle and the war that go somewhat unnoticed to many of us. After all, visitors love to learn about Pickett’s Charge, and it is important to continue to interpret the popular parts of the battlefield. For example, Gettysburg National Military Park is meeting visitor needs by presenting three ranger programs this fall between Cemetery Ridge, Little Round Top, and the Third day as a whole. It is important that we continue to tell the stories of these better-known sites, as it draws audiences in and makes them excited to learn more about the park and its history.

But stories like that of Dennis Mahan and his teachings also help us understand the war at a more detailed level. Due to time constraints and an overwhelming amount of content to cover in the classroom, the way Civil War history is taught can be confusing, and the maturation of leaders is a subject that we tend to save for figures like Lincoln and Grant. While some commanders definitely had an “X factor,” most were not born the strategists they became by the end of their careers. The great soldiers of the war honed their skills over a series of events. For many commanders, it began in the West Point lecture hall. Those young men then quickly found themselves in their first field test in Mexico. Not all of them stayed on a military track: Grant left the military and saw failures like the failed business and sickness that shaped him into the man we remember today, while Meade continued his military training and worked on topographical research. By the time the war started, Mahan’s students had a wide variety of experiences under their belts and began to piece together their lessons, a process that culminated in some of the greatest battles in American history.


Sources

Ranger Programs at Gettysburg.” National Park Service. Accessed October 31, 2017

Phipps, Michael. “Mahan at West Point, ‘Gallic Bias,’ and the ‘Old Army’”: The Subconscious of Leadership at Gettysburg.” National Park Service

Cullum, George. “Dennis H. Mahan.” Biographical Register of the Officers and Graduates of the United States Military Academy at West Point, New York. Accessed October 31. 2017.

The Fragility of History: William H. Harris’ West Point 1861 Album

By Logan Tapscott ’14

Musselman Library’s Special Collections & College Archives  at Gettysburg College is a center for undergraduate student and faculty research and houses and maintains several types of primary source materials, including rare books, letters, diaries, maps, works of art, and photographs. Carolyn Sautter, the director of Special Collections, said, “one of the best ways of learning about historical eras is to actually see the images of the time period.” Special Collections provides researchers and visitors opportunities to visually engage with objects through either the exhibit cases in the Collection’s Reading Room or on the GettDigital website, a venue on which poeple can explore the Civil war by seeing peoples’ faces. Especially with fragile materials such as William H. Harris’ West Point 1861 Album, Special Collections’ online resource provides access to objects that would otherwise be inaccessable to students and faculty.

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Bravely on the Battlefield: 1st Lieutenant George A. Woodruff

Throughout the Civil War, many West Point graduates chose either to fight for or against the United States. In the first days of July 1863, many of these West Pointers fought against each other on the battlefield in Gettysburg, and many of them lo…

This post was first published on the Civil War Institute’s previous blog901 Stories from Gettysburg.
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Throughout the Civil War, many West Point graduates chose either to fight for or against the United States. In the first days of July 1863, many of these West Pointers fought against each other on the battlefield in Gettysburg, and many of them lost their lives. One particular West Point graduate, 1st Lieutenant George A. Woodruff, fought bravely during the battle but lost his life on July 4th after being mortally wounded during Pickett’s Charge on July 3rd. He was a member of Battery I, 1st United States Light Artillery. While he never saw the end of the Civil War, Woodruff contributed to the Union’s victory through his actions on those three days in Gettysburg.

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