Final answer:
Artillery had the most lasting impact on future warfare from World War I, transforming battlefield tactics with its power and accuracy. Tanks, introduced by the British, also significantly shaped modern military tactics.
Step-by-step explanation:
The Weapon with the Most Lasting Impact on Future Warfare
Among the weapons introduced in World War I, artillery left the most lasting impact on future warfare. The increasing power and accuracy of artillery transformed the battlefield, accounting for the majority of combat deaths. Artillery's importance continued to grow into subsequent conflicts, with advancements in firepower and technology making it a cornerstone of modern warfare. The British introduced the tank in World War I, another major innovation, which also had a profound long-term effect on warfare.
Moreover, the use of machine guns, with their rapid-fire capability, fundamentally changed infantry tactics and forced the implementation of defensive strategies such as trench warfare. While other technologies like poison gas and flamethrowers had significant psychological impact and changed battlefield dynamics, the sustained influence of artillery and the introduction of tanks have had far-reaching effects on how wars are fought to this day.