The Stockholm Pact, also known as the Baltic Sea Pact, or, unofficially, the Baltic Alliance was an agreement signed by Prussia and Sweden in 1819 to form a Mutual Protection Pact, due to the growth of Napoleonic France and the increasing belligerency of the Russian Empire. The United Kingdom joined in 1822.
While not officially called an "alliance" by the three nations that were party to the agreement, Russia and France took it to be so, so tread carefully, not wishing to bring war back to Europe after the massive destruction of the First Great European War. However, the anger of Great Britain and Prussia lead the two to agree to support each other in an attempt to wrestle land from France: Prussia wish ed to expand into the Confederation of the Rhine , while at the same time destroying Poland due to the Eastern European nations alliance with France through the Marseilles Pact, while Great Britain wished to halt France's colonial ambitions in Africa.
Prussian Expansion War
The result of this planning was the Prussian Expansion War, which resulted in the defeat of the Stockholm Pact, after France, Italy and Austria-Hungary was able to mount a successful counter-attack and defeated the Prussian Armies, while the French Navy was able to penetrate and eventually destroy the Royal Navy blockade of France, and was able to stop a large majority of the shipping between Great Britain and the rest of the world, nearly starving and bankrupting the United Kingdom. But the death knell was sounded when Russia, fresh from its victory in the Black Sea War, attacked both Sweden and Prussia, annexing a large part of Northern Sweden and East Prussia, including the city of Koenigsberg. Prussia and Britain surrendered soon after, and were forced to sign the Treaty of Vienna, which took away the small North Sea coastline that Prussia held and gave it to the Confederation of the Rhine, while Poland and Austria-Hungary was also able to capture some Prussian territory. Great Britain had to surrender Cyprus and Jamaica, in return for a small payment, to France.
The Stockholm Pact was quietly done away with after the Prussian Expansion War, with Sweden, who never heard of Britain's or Prussia's war plans, falling into France's Sphere of Influence in anger. Prussia and the United Kingdom eventually formed the United Coalition in 1846, which eventually included Austria-Hungary, Spain and the Ottoman Empire as well, and would be the victorious alliance in the Second Great European War.