The mounted cavalry needed the extra reach that the spatha afforded to reach the infantry from the top of a horse. The semispatha was also in use at the same time for another reason. A short blade is much better suited for fighting against a long sword, when in the hands of a skilled soldier. The quick delivery of a stab to the face or stomach was still a favored method of executing the enemy. The warrior just had to step inside of the enemy s guard and kill him.
Short swords are also less tiring when used in conjunction with a shield.
From purifying the ore, to tempering the blade it was a talent that took no small amount of skill. The iron versus steel question is moot, since steel definitely was used, though not by design. The evolution of the sword was another facet of the history of the Roman sword. The Roman sword went through many changes, which were reflected in the manner in which the swords was employed. Roman Military Equipment .