What major technological advancement was first significantly utilized in World War I?

The first significant use of tanks occurred during World War I, marking a major advancement in military technology. Prior to this, combat relied heavily on infantry and cavalry, leading to devastating trench warfare characterized by stalemate and high casualties. The introduction of tanks provided a solution to these issues by combining mobility with firepower, enabling forces to break through enemy trenches and fortifications. Tanks were first used by the British in the Battle of the Somme in 1916, and their deployment altered the dynamics of ground warfare.

While aircraft carriers and jet fighters represent significant advancements in naval and aerial warfare, respectively, they were not prominent or even in existence during World War I. Submarines had been in use prior to the war, but their role was still evolving, and they did not have the same transformative impact on battlefield tactics as tanks did during this period. Thus, tanks stand out as the significant military innovation of World War I, influencing future combat strategies and technologies.