Book excerpt: Following World War I, horse cavalry entered a period during which it fought for its very existence against mechanized vehicles. On the Western Front, the stalemate of trench warfare became the defining image of the war throughout the world. While horse cavalry remained idle in France, the invention of the tank and its potential for success led many non-cavalry officers to accept the notion that the era of horse cavalry had passed. During the interwar period, a struggle raged within the U.S. Cavalry regarding its future role, equipment, and organization. Some cavalry officers argued that mechanized vehicles supplanted horses as the primary means of combat mobility within the cavalry, while others believed that the horse continued to occupy that role. The response of prominent cavalry officers to this struggle influenced the form and function of the U.S. Cavalry during World War II.