Machine guns are capable of firing hundreds of bullets per minute as opposed to the one bullet at a time firing from rifles. The introduction of machine guns into war changed battlefield tactics and led to the development of trench warfare. Prior to World War 1 and machine guns soldiers would charge in a wave against the opposing forces but this type of strategy was immediately abandoned due to enormous casualties. Soldiers had to attack and defend using trenches and fortifications which also slowed the pace of battles.
