The spatha, or long sword, was originally the weapon of the Roman cavalry units. Longer than the infantry gladius, it gave the reach and cutting power needed from horseback. In the 3rd and 4th centuries, the spatha gradually replaced the gladius as the infantry sword, probably due to the large numbers of Celtic/Germanic recruits that then populated the legions in the late Empire.

The spatha is also credited with being the inspiration for the development of the Migration era sword styles - in fact, in many bog finds it is difficult to determine which swords are late Roman spathae and which are native Germanic swords.