What is required for mercantilism to occur?

A requirement for mercantilism is an active Government policy aimed at creating a positive trade balance for their own country: that is, simply said, earning more money by selling and exporting goods than spending money on imported goods from other countries. Importing goods is only 'good' in mercantilism if you can sell them on to other countries at a profit. That is the reason that some countries tried to 'corner' markets such as the sugar market, the spices market, the grain market etc.