How did they train?

Roman legion training was incredibly arduous. Other than hand-to-hand combat training with wooden weaponry (often twice as heavy as the actual steel implements used in battle), legionaries were expected to regularly complete both an 18.4 mile (20 Roman miles) march for new recruits or a 22 miles (roughly 24 Roman miles) for more seasoned recruits, both in under 5 hours. Training also consisted of learning battle formations and how to follow commands.

Once initial training was completed, newly fledged legionaries had to swear an oath to the Roman people (and, later, the emperor).