Wikipedia
Tirones
Tirones were new recruits in the armies of the Roman Empire. A tiro could take up to six months before becoming a full miles (infantryman/private).
In the 4th century, Vegetius describes his ideal, rigorous training, in contrast to the lax habits of his own day:
"Of aspirants for enlistment were required good eyes and sound and vigorous bodies; but no definite height, certain units excepted, seems to have been prescribed... After taking the oath ( sacramentum), the recruits entered upon an intensive and apparently endless course of training. The success of Roman arms, like all others, came from drill, discipline and training."