This thesis examines how the modern weaponry shaped the American soldiers’ use of weaponry and the change of tactics during World War I. The American experience was unique as Britain, France, and Germany grew accustomed to the advancements in weaponry over time, while the American Expeditionary Force encountered this type of warfare for the first time. The American Army served mainly as a constabulary, fighting guerilla forces before the war, and had to be trained to fight a conventional war in Europe. The common soldiers would modify official doctrine to fit the realities of the battlefield in which they found themselves.