The Star League Defense Force (SLDF) was a military organization in the fictional universe of the BattleTech franchise. Established during the Star League era, it served as the primary defense force for the Inner Sphere, uniting various factions to maintain peace and stability across the galaxy. The SLDF was known for its advanced technology and well-trained personnel, playing a crucial role in the defense against external threats. The SLDF was disbanded following the Amaris Civil War, leading to a power vacuum and the eventual decline of the Star League. Its legacy continues to influence the political and military landscape of the BattleTech universe, with remnants of the force still impacting events in later timelines.