What do appellate courts do?

Explanation:

they are empowered to hear an appeal of a trial court or other lower tribunal.

Appellate courts are the part of the judicial system that is responsible for hearing and reviewing appeals from legal cases that have already been heard in a trial-level or other lower court. - Investopedia

first, the romans stayed isolated because they had to defend their own territories from neighboring cities that were harassing them, like the etruscans. second, once the romans managed to defeat their neighbors, and started to expand their territory, they started to build roads and bridges. finally, now that the romans have covered their territory with roads functioning as highways, they could mobilize their legions faster to assemble larger military units in a specific place.