Most books and documentaries about the war focus on the carnage of the trenches, depicting the ceaseless bombardment and sniping, and the assaults and counterattacks that took millions of lives. This was the experience of most frontline soldiers during that great conflict, but it was not the only experience. There was another war going on beneath the trenches, a war of tunnels and mines fought by men who didn't see sunlight for days at a time and who lived in constant fear of cave-ins and enemy detection. These men, who had mostly been miners in civilian life, lived a twilight existence, working long hours in silence and near darkness while great battles raged overhead. They suffered from fatigue, stress, and the knowledge that they could be killed at any time by an unseen enemy. Despite this, they persevered, and the mines they laid under enemy trench systems turned the tide of at least one major battle. 

The sleek hunter-killers lurking beneath the waves, using periscopes to close in unnoticed on their prey, added a new, nerve-wracking element to naval warfare. The mere threat of submarine attack immediately altered naval tactics and strategies employed by both the Western Allies and the Central Powers, shifting them towards a more cautious approach, especially at the war's start when the submarine threat remained untested. During World War I, German U-boats operated solo except on one occasion. Initially, the British and nations supplying England with food and materiel scattered vessels singly across the ocean, making them vulnerable to the lone submarines. However, widespread late war re-adoption of the convoy system tipped the odds in the surface ships' favor.