The Triarii were a key component of the Roman army during the Republic era. They formed the third line of the Roman infantry, positioned behind the Hastati and Principes. Typically composed of experienced soldiers, the Triarii were equipped with heavy armor and long spears, making them formidable in battle. Their role was to provide support and stability, often being called upon in critical moments of combat. In battle formations, the Triarii were known for their disciplined and steady approach. When the front lines faltered, they would step forward to reinforce the troops, embodying the phrase "in extremis" or "in the last resort." This made them essential for maintaining the effectiveness of the Roman military strategy.