The Roman Legions were the military units of the ancient Roman Empire, known for their discipline, organization, and effectiveness in battle. Each legion typically consisted of about 4,500 to 6,000 soldiers, primarily heavy infantry, and was divided into smaller groups called cohorts and centuries. The legions played a crucial role in expanding and protecting the empire's vast territories. Legionaries, the soldiers of the legions, were well-trained and equipped with weapons like the gladius (a short sword) and pilum (a throwing spear). They also built fortifications and roads, contributing to the infrastructure of the empire. The legacy of the Roman legions continues to influence modern military organizations.