A shallow, nearly enclosed sea
The Baltic is a brackish, shallow sea connected to the North Sea by the narrow Danish straits, including the Øresund between Denmark and Sweden. It is also seasonally affected by ice, especially in the north and east, which has long limited winter sailing. These conditions gave the Baltic a particular character. It was a region where trade and war were heavily influenced by a few chokepoints, and where the rivers feeding into it created routes deep into eastern Europe.
Viking-age routes
From about the eighth century, Scandinavian seafarers and traders were active around the Baltic. Trading centres such as Hedeby, in what is now northern Germany, and Birka, in Sweden, connected the western Baltic with the North Sea, while settlements further east, including Staraya Ladoga, linked the sea to inland river routes. Scandinavian travellers, often called the Rus in written sources, used the rivers of eastern Europe to reach the Black Sea and Constantinople as well as the Caspian region, carrying furs, slaves, amber and other goods and receiving silver coin and luxuries in return. Large numbers of Islamic silver coins, called dirhams, have been found in Baltic hoards, especially in Gotland, which supports the picture of a trade network reaching far to the southeast.
The vessels involved are known mainly from archaeology and from finds such as the Viking ships at Roskilde in Denmark, where several wrecks were recovered. They included clinker-built longship types for warfare and broader, deeper cargo ships for carrying goods. The Norse seafaring skill that made these routes workable depended on shipbuilding traditions that were shared across the whole Baltic and North Sea region.
The rise of the Hanseatic League
In the later Middle Ages, control of Baltic trade passed to merchant communities in northern German towns. Lübeck, founded in the twelfth century on a site chosen for its position near the western Baltic, became the most important of these. Merchants from many towns formed associations to protect their interests abroad, and from the thirteenth century these developed into the loose network now known as the Hanseatic League, which included Lübeck, Hamburg, Danzig (Gdańsk), Riga, Stralsund and many others. It was not a state with a unified fleet or government, and historians continue to debate how formally it should be defined.
The Hanseatic trade moved bulky goods that northern and western Europe needed: grain from Prussia and Poland, timber, tar and pitch, furs, wax and fish, as well as salt, cloth and metalwork travelling the other way. The league maintained overseas offices, known as kontore, in places such as London, Bruges, Bergen and Novgorod. The network of Hanseatic ports is covered separately, but the role of the Baltic as its main sea should be stressed here. The Treaty of Stralsund in 1370, which ended a war between the league and Denmark, is often taken as a high point of Hanseatic influence.
The cog
The ship most associated with Hanseatic trade is the cog. It was a single-masted, square-rigged vessel with a flat bottom, steep sides and a stern-mounted rudder, a design well suited to carrying large cargoes in the shallow harbours of the northern coast. Cogs were generally built with overlapping planks, and in the later medieval period they sometimes carried raised platforms at the bow and stern, which could be used in defence. The best-known surviving example is the Bremen cog, found in the River Weser in 1962 and dated by tree rings to around 1380. Its discovery greatly improved knowledge of how such vessels were built. Later in the Middle Ages, cogs were gradually replaced by other types such as the hulk and, in the fifteenth and sixteenth centuries, the carrack-like ships and larger vessels of the early modern period.
Dutch carriers and the Sound
From the fifteenth and sixteenth centuries, Dutch shipowners increasingly took over the carrying of Baltic grain and timber to western Europe, partly because their ships were economical and cheaply operated. Denmark controlled the Øresund, and from the fifteenth century it collected tolls from passing ships, known as the Sound Dues; these continued until 1857, when an international agreement ended them. Control of the straits was therefore both a source of revenue and a source of friction between Denmark and its neighbours.
Naval rivalry in the early modern Baltic
From the sixteenth century the Baltic was a theatre of competition between Denmark-Norway, Sweden, Poland-Lithuania and, increasingly, Russia. Sweden built up a large navy during its seventeenth-century period as a great power, and the Vasa warship, which sank on its maiden voyage in 1628, was part of that expansion. The Great Northern War (1700–1721) ended Swedish dominance. Peter the Great of Russia founded St Petersburg in 1703 on the Gulf of Finland and built a Baltic fleet; the Russian naval victory at Gangut (Hanko) in 1714 was an early success of that fleet. By the end of the war Russia had become the leading Baltic power, with Sweden and Denmark in a lesser role.
Later episodes include the British attack on the Danish fleet at Copenhagen in 1801 and 1807, when Britain sought to prevent Baltic naval resources from serving its enemies, and the activities of fleets during the world wars. In the Cold War, the Baltic was divided between NATO and Warsaw Pact states. Since the early 1990s the independence of the Baltic states and the later accession of Finland and Sweden to NATO have again changed the strategic picture, a subject that is still developing.
Legacy
The Baltic remains one of the busiest seas for shipping, with ferries, bulk cargo and oil moving from ports such as Gdańsk, Rostock, Gothenburg, Stockholm, Helsinki and St Petersburg. The long history shows a pattern: a shallow sea with a narrow entrance, rich in timber, grain and fish, whose rulers and merchants repeatedly competed for control of the routes that connected northern Europe to the wider world.