Because of the Christianity adopted in the country as the official and uniform religion for all, Roman soldiers began to wear large cast crosses around their necks. And the fact that, starting from the 4th century, not infantrymen, but cavalry and archers began to play an increasing role in battles. Also, the fact that the armor of the legionnaires has become much heavier and more reliable.
One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.