Why did european merchants concerned about the supply gold and silver

European merchants concerned about the supply of gold and silver because, during mercantilism, both precious metals became the main value shelters used by countries to accumulate wealth. In addition, the imposition of the gold standard as a means of monetary valuation implied that countries would tend to accumulate this metal to give strength to their respective currencies and, therefore, to their economies.

Then, according to the mercantilist economic organization and the gold standard, the more gold and silver a country had accumulated in its reserves, the stronger its economy would be and the ability to establish commercial conditions for the rest of the nations.

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.