Though initiated by the Danish conquest of Gotland, the war quickly spread to encompass all territories where Denmark and the Hansa had conflicting claims.

The resulting treaty, signed at Stralsund, secured the Hanseatic League's position as a great power in Northern Europe.

[2] The region was also an important distribution center for goods transferring from the Baltic to the North Sea, for the Oresund passed between Scania and the Danish island of Sjælland.

[4] Valdemar, who had just managed to stabilize his kingdom after the catastrophic reign of Christopher II, had ambitions to further expand his Danish realm to become a new northern great power.

Gutnish militia attempted to fend off the invasion, but they stood little chance against Valdemar's experienced army of mercenaries.

Visby, the largest and most prominent city on the island, surrendered to Valdemar, paying a huge sum of tribute in order to prevent a sacking.

The Dutch and Teutonic cities in particular were guilty of this, as despite providing financial subsidies to the Hansa, still continued trade with the Danish.

Valdemar took the opportunity and attacked the Hanseatic navy, and succeeded in capturing 12 ships in the ensuing Battle of Helsingborg.

The Confederation, bolstered by alliances with Sweden, Mecklenburg, and Holstein, resumed hostilities against Valdemar, who now also had to deal with rebellious nobility.

When Helsingborg was captured in September, 1369, the Danish council sued for peace, and the Treaty of Stralsund was negotiated in the following year.

More important was the acquisition of four key forts (Malmo, Helsingborg, Skanor and Falsterbo), which granted the Hanseatic League complete de facto control over the Oresund.

The war proved that the Hanseatic League was capable of militarily challenging foes by raising its own armies and navies.