Which two examples of modern military technology had the greatest impact on the course of World War I?

Technology during World War I (1914-1918) reflected a trend toward industrialism and the application of mass-productionmethods to weapons and to the technology of warfare in general. This trend began at least fifty years prior to World War Iduring the American Civil War of 1861-1865,[1] and continued through many smaller conflicts in which soldiers and strategists tested new weapons.

One could characterize the earlier years of the First World War as a clash of 20th-century technology with 19th-century warfare in the form of ineffective battles with huge numbers of casualties on both sides. On land, only in the final year of the war did the major armies made effective steps in revolutionizing matters of command and control and tactics to adapt to the modern battlefield and start to harness the myriad new technologies to effective military purposes. Tactical reorganizations (such as shifting the focus of command from the 100 + man company to the 10 + man squad) went hand-in-hand with armored cars, the first submachine guns, and automatic rifles that a single individual soldier could carry and use.