A Roman Legion was a large military unit of the ancient Roman Empire, typically consisting of about 4,000 to 6,000 soldiers. Each legion was made up of infantry, cavalry, and support troops, organized into smaller groups called cohorts and centuries. The legions were known for their discipline, training, and effective tactics, which contributed to the expansion and protection of the empire. Legionaries, the soldiers of a legion, were usually Roman citizens who served for a term of around 25 years. They were equipped with standardized weapons and armor, including the gladius (a short sword) and the scutum (a large shield). The success of the Roman legions played a crucial role in establishing and maintaining Roman control over vast territories.