The infantry in the American Civil War comprised foot-soldiers who fought primarily with small arms and carried the brunt of the fighting on battlefields across the United States. The vast majority of soldiers on both sides of the Civil War fought as infantry and were overwhelmingly volunteers who joined and fought for a variety of reasons. Early in the war, there was great variety in how infantry units were organized and equipped - many copied famous European formations such as the Zouaves - but as time progressed there was more uniformity in their arms and equipment.
Historians have debated whether the evolution of infantry tactics between 1861 and 1865 marked a seminal point in the evolution of warfare. The conventional narrative is that officers adhered stubbornly to the tactics of the Napoleonic Wars, in which armies employed linear formations and favored open fields over the usage of cover. However, the greater accuracy and range of the rifle musket rendered these tactics obsolete. The result was greater casualties and increasing usage of trench warfare, presaging the course of future conflicts. More recent scholarship has challenged this viewpoint and argued the impact of the rifled musket was minimal. In this interpretation, the tactics used remained practical and the decisiveness of battles was affected by other factors.
This debate has implications not only for the nature of the soldier's experience, but also for the broader question of the Civil War's relative modernity. Williamson Murray and Wayne Wei-Siang Hsieh argue that the conflict was resulted from "the combination...of the Industrial Revolution and French Revolution [which] allowed the opposing sides to mobilize immense numbers of soldiers while projecting military power over great distances."
Outbreak of war
At the start of the war, the entire United States Army consisted of 16,367 men of all branches, with infantry representing the vast majority of this total. Some of these infantrymen had seen considerable combat experience in the Mexican–American War, as well as in the West in various encounters, including the Utah War and several campaigns against Indians. However, the majority spent their time on garrison or fatigue duty. In general, the majority of the infantry officers were graduates of military schools such as the United States Military Academy.
In some cases, individual states, such as New York, had previously organized formal militia infantry regiments, originally to fight Indians in many cases, but by 1861, they existed mostly for social camaraderie and parades. These organizations were more prevalent in the South, where hundreds of small local militia companies existed to protect against slave insurrections.
With the secession of eleven Southern states by early 1861 following the election of President Abraham Lincoln, tens of thousands of Southern men flocked to hastily organized companies, which were soon formed into regiments, brigades, and small armies, forming the genesis of the Confederate States Army (CSA). Lincoln responded by issuing a call for 75,000 volunteers, and later even more, to put down the rebellion, and the Northern states responded. The resulting forces came to be known as the Volunteer Army versus the professional Regular Army. More than seventeen hundred state volunteer regiments were raised for the Union Army throughout the war. In all, approximately 80% of Union soldiers fought as infantry, while 75% of Confederate soldiers were infantry.
Organization
The regiment was the foundational unit for mustering, training and maneuvering infantry during the Civil War. The typical infantry regiment nominally consisted of about 1,000 soldiers organized into ten companies. It was commanded by a colonel (assisted by a lieutenant colonel and at least one major), with a dedicated headquarters and a band of musicians (the band later removed). Regiments were designated by a number and the name of the state that raised them, such as the 10th New York or 48th Mississippi. Each regiment also had their regimental colors, flags which not only served to denote position and alignment on the battlefield but which held special emotional significance. To be chosen as the color guard charged with protecting these flags was a special honor, and one of the most dangerous positions in the regiment.