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The Trade Cog is a small civilian vessel available in Age of Empires II that accumulates Gold for the player's civilization by sailing between their own and a friendly or neutral player's Dock. It can also trade with enemy Docks, though this is dangerous, as the Trade Cog lacks any offensive or defensive capabilities.
This unit is similar to the Trade Cart as it gains Gold for whoever is using it. Unlike the Trade Boat from Age of Empires, the units do not need to pay resources to gain gold. Caravan, a technology researched at the Market, makes both units move twice as fast.
The demands of trade along the northern coasts of Europe led to the development of new types of ships with wide beams, deep drafts, square sails, stern rudders, and large cargo space. Ships of this new design were called cogs and they dominated Middle Age sea commerce from the Baltic Sea to the Western Mediterranean. Because these ships could not be drawn up on a beach easily, ports required piers extending out into water sufficiently deep to keep the cogs afloat. The Far Eastern equivalent to the trade cog was the Chinese junk, a much more advanced ship not surpassed in the West for many centuries.