Complex sentence: The spatha was a longer double-edged sword initially used only by Roman Cavalry units; however by the 2nd century A.D. the spatha was used throughout much of the Roman Empire's legionary soldiers were heavily trained and prided themselves on their disciplinary skills.
Split into simpler sentences: The spatha was a longer double-edged sword initially used only by Roman Cavalry units; however by the 2nd century A.D. the spatha was used throughout much of the Roman Empire. The Empire's legionary soldiers were heavily trained and prided themselves on their disciplinary skills.