18. Before nationalism, people would have identified as primarily belonging to

Religion.

Explanation:

Before the advent of nationalism in the nineteenth century, the main criteria for identifying larger groups was religion. This became especially established during the 16th century until the Napoleonic Wars. During the 16th century, several different Catholic factions emerged formed by a movement historically known as the Reformation.

it wanted to boycott trade with enemy nations.

i can't beat you to a pulp if i'm not close enough.