The Hansa is not a state with a single founding date; it is a network of merchants and towns woven together gradually from the 13th century onwards. A mutual-protection pact between Lübeck and Hamburg in 1241 secured the land corridor that linked Baltic salt with North Sea fish, and that nucleus expanded rapidly. Bremen, Danzig (Gdańsk), Riga, Reval (Tallinn), Visby and others joined in turn. The first general diet (Hansetag) at Lübeck in 1356 is the concrete moment when the structure becomes legible: this was no longer a collection of merchant guilds, but a confederation of towns.

The Hansa's economic power was tightly tied to the geography of its day. The Baltic supplied grain, timber, furs, beeswax and resin; Bergen, dried cod and other fish; Novgorod, Russian furs; Flanders and England, wool and woven cloth; Lüneburg, salt. The vessel that carried all of this was the *cog* — a high-sided, broad-holed, wind-efficient ship that moved a large cargo with a small crew, and dominated northern European maritime trade for decades. The Hansa's foreign 'kontors' — the Steelyard in London, and the four great kontors at Bruges, Bergen and Novgorod — operated like enclosed merchant colonies, with shared warehouses, shared law and shared discipline.

This network was also politically organised. Between 1361 and 1370 the Hansa defeated King Valdemar IV of Denmark and imposed the Treaty of Stralsund (1370), winning privileges over the passage of the Sound — for a merchant league to force a kingdom to its knees was a remarkable event in its century. Even so, the Hansa never had a single flag, a standing army or a common tax. Decisions were taken only at periodic Hansetag meetings, and member towns could refuse to comply if they wished. This was its flexibility — and its permanent weakness.

In the 16th century two large shifts moved the ground under the Hansa. On one side, the rising centralised national states (Denmark, Sweden, England, the Dutch Republic, Russia) began to find the independent foreign policy of merchant towns intolerable. On the other, Atlantic trade — sugar, silver, Indian Ocean spices — moved the economic centre of gravity from the Mediterranean–North Sea axis to Lisbon, Seville, Antwerp and Amsterdam. The Hansa steadily lost members; the last Hansetag met in 1669, after which only Lübeck, Hamburg and Bremen kept the honorary title. The Hansa's real legacy is not an empire but a model: history's first large-scale demonstration of how cities, without a state, by contract alone, can do business at continental scale.