Superconductors proved to be useful for moving things at high speed and low cost, which didn't escape attention of military engineers. An electromagnetic cannon was an old idea, but never before was it possible to propel a missile strongly enough to make it worthwhile - the energy cost was enormous, which made the weapon completely impractical. With superconductors though, things have changed: an electromagnetic gun could suddenly compete against traditional cannons based on explosives (with range and power limited by durability of the material used for the barrel) and energy beams (which were limited to sight range, and never really packed much "oomph" anyway). Large electromagnetic guns quickly dominated the battlefields, being expensive to produce but very cheap and easy to run; also, their power and range were unmatched. They normally fired explosive shells, but they could propel any payload - as long as it was encased in a ferromagnetic capsule.