The Roman Empire was very advanced for the time, and it left such a huge imprint on the civilization even centuries, and thousands of years after it.

The organization was a different scale.

Fun fact: Some of the most famous battles in England in the middle ages, such as battle of Hasting, were basically 5k - 9k soldiers in each side. That's just one and a half Roman legion.

Rome, could field 12 legions at a time, and the scale was insane. I can see why the Roman Empire remained such a symbol of civilization for a thousand of years after its fall.