How did knights obtain ownership of land

By gaining them from their seniors or through participation in war.

Explanation:

In the feudal system, a ruler or a senior would distribute his land to his vassals. They all had certain obligation to fulfill. That was to pay taxes and to participate in wars in the name of their senior. If this wars were successful it was a normal thing for a ruler to give a part of taken land to their knights in return.

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