The Baltic is not usually a sea one associates with activities by the Royal Navy, yet for three centuries it was a region for the navy’s work, if in a less than usually violent form. Apart from battles at the entrance, there were few instances where the navy was used in its aggressive role, for once into the sea – past the barrier of the entrance at Copenhagen – opposition tended to hunker down into its ports and let the navy rule the sea at least while it was present. As soon as it was gone, the local forces reappeared. The role of the Royal Navy in the Baltic was thus one of intermittent interventions, best characterized, in Admiral Jackie Fisher’s term, as ‘Baltic cruises’. The purpose of the navy in the first century and a half of its activity in the Baltic was above all to supervise and protect the trade of the sea, much of which was in goods that were required for the navy itself to function. The trading involvement of British ships preceded the navy’s presence by centuries, and developed slowly and, for Britain, in a typical pattern that can be paralleled in other seas; the combination of the threat of force and the exercise of trade was prefigured long before the Royal Navy came into existence in the actions of King Knut and in the accounts of two traders who visited King Alfred’s court.

The Baltic Sea is one of the enclosed seas that surround Europe on three sides. The North Sea, the Irish Sea and the English Channel have wide and open entrances, which communicate easily with the outer Atlantic Ocean; the Black Sea, the Mediterranean and the Baltic Seas all have narrow and difficult connections with the oceans, and these chokepoints allow states to control those passages. For the Baltic the connecting passage is in two parts. The three narrow Danish Straits run through the Danish islands, the Sound between Sjaelland and the Swedish mainland of Skåne, the Great Belt between Sjaelland and Fyn, the Little Belt between Fyn and the Jutland peninsula. In the twentieth century these have all been bridged, and the Kiel Canal has been cut through the base of the peninsula, replacing two earlier canals, which has supplemented the older access routes, but the Sound is still the main route from the Atlantic Ocean into the Baltic Sea.