Final answer:
The Civil War's deadliness was largely due to rapid advancements in military technology, particularly in logistics and weaponry, while strategies and medicine lagged behind. Railroads, steamboats, and the electric telegraph revolutionized movement and communication, and deadly artillery pieces made traditional battle tactics obsolete.
Step-by-step explanation:
The rapid advancement in military technology before and during the Civil War greatly impacted the conflict's lethality. While military strategies and medicine did not see significant development at the time, innovations such as railroads, steamboats, and the electric telegraph transformed logistics and communication.
The Industrial Revolution enabled the North's superior production capability, leading to an excess in war materiel and more efficient troop mobilization. Further, the introduction of more lethal weapons, such as accurate and rapid-firing artillery pieces, increased combat fatalities significantly, making infantry charges and cavalry tactics outdated and often futile in the face of such firepower.