Gulf of Tonkin

The Gulf of Tonkin connected the ports and river mouths of northern Vietnam with southern China, Japan and the wider Asian trading world. In the seventeenth century ships reached the trading centres of Tonkin through its coastal approaches, including the anchorage at Domea near the river mouth. River transport then linked the coast with Phố Hiến and Thăng Long.

The Dutch East India Company established commercial and diplomatic relations with Tonkin in 1637. Silk purchased there entered the company's trade with Japan, tying northern Vietnamese production to the movement of silver and other goods across East Asian seas. The relationship lasted until 1700. A letter from the king of Tonkin dated 10 February that year concerned the termination of trade with the company. Its surviving record marks the end of one particular commercial arrangement within a gulf whose maritime connections extended far beyond European merchants.