Complex sentence: This sword design eventually led to the development of the civilian rapier, but it was not replaced by it, and the Side-sword continued to be used during the rapier's lifetime.
Split into simpler sentences: This sword design eventually led to the development of the civilian rapier, but it was not replaced by it. While correct to call it an "early rapier" since it gave birth to the true rapier, it continued to be used during the rapier's lifetime.