One of the most important breakthroughs in military technology associated with World War I, and certainly the one that continues to capture the public imagination, was the introduction of a war machine that came to dominate the face of land battles throughout most of the 20th century: the tank. As a concept, it was not revolutionary; in fact, it harkened back to classical antiquity and to the Middle Ages, such as the covered battering rams and testudos which had made frequent appearances on ancient battlefields. In essence, it was designed to solve the age-old problem of protecting infantry from enemy projectiles while remaining mobile.