not a full-blown trade theory (see above); rather,
an economic policy of governmental accumulation of wealth, in the form of gold bouillon for:
domestic control
investment
international expansion
reflects the era of nation-building and the shifting of European political power from feudal lords and the church to national sovereigns; also reflects and supports the principal source of wealth -- trading
The trade-policy implication of this economic policy was the generation of a national trade surplus, paid for by accumulation of gold reserves.
Before fully developed financial systems, there was little international credit. Therefore, a current-account surplus was not matched by net capital outflow (net loans or investment overseas); rather, it was matched by a net inflow of gold to pay for the excess of goods exported from the country. Some of this gold found its way to overseas investment by the sovereign.