When groups of people are displaced to a new country because they flee in fear of their lives from their homeland, they might choose to settle together in a community in a new location and try to maintain their ethnic identity. This demonstrates the concept of .

refugee

Explanation:

they are fleeing a war or some sort of threat not leaving for pleasure, which is immigration

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