What innovation was essential for communication in the trenches?

Carrier pigeons

During World War I, carrier pigeons played a crucial role as reliable and fast messengers, capable of crossing enemy lines where modern communication means often failed. A pigeon named "Cher Ami" was even decorated for delivering a vital message that saved nearly 200 men from an encircled American battalion. These heroic birds demonstrated human ingenuity in the face of the challenges of war, and their service underscored the importance of reliable communication under the most extreme conditions.