Final answer:
A key problem faced by both sides during World War I was the lack of resources, including the shortages of food and military supplies that severely impacted soldiers' effectiveness and morale, especially in Russia.
Step-by-step explanation:
A key problem that both sides faced during World War I was lack of resources. During the conflict, all nations involved struggled with supply shortages, which significantly affected their military operations. For instance, Russia experienced a devastating scarcity in supplies, leading to dire consequences for its troops. Inadequate supplies of guns and munitions, as well as food shortages at home, crippled the Russian army's effectiveness and morale. Soldiers on the front line were all too aware of the hardships faced by their families back home, including long lines and riots due to the scarcity of necessities. The Tsarist government also failed to manage the war effort efficiently. This shortage of essential resources was one of the many challenges faced by the countries involved in World War I, contributing to the overall grueling nature of the war.