From the latter half of the 13th century to the 15th century, the crusading Teutonic Knights ruled over the lands of Prussia through their monastic state. The Knights' expansionist policies brought them into conflict with the newly-reunited Kingdom of Poland and embroiled them in several wars, culminating in the Polish-Lithuanian-Teutonic War, whereby the united armies of Poland and Lithuania, bolsted by Bohemian mercenaries, defeated the Teutonic Order at the Battle of Grunwald in 1410. Its defeat was formalised in the Second Treaty of Thorn in 1466 ending the Thirteen Years' War, leaving western Prussia under Polish control as the province of Royal Prussia and eastern Prussia remaining under the knights, but as a fief of Poland.



The Teutonic Order lost eastern Prussia when, with the advance of Lutheranism, Grand Master Albert of Brandenburg-Ansbach secularized the Prussian branch of the Teutonic Order in 1525, after having converted to Lutheran Protestantism, establishing himself as Duke Albert of Prussia and a vassal of the Polish crown. Walther von Cronberg, the next Grand Master, was enfeoffed with the title to Prussia after the Diet of Augsburg in 1530, but the Order never regained possession of the territory. Albert's line died out in 1618, and Ducal Prussia passed to the Electors of Brandenburg, forming Brandenburg-Prussia. Through the Treaties of Wehlau, Labiau, and Oliva, Elector and Duke Frederick William succeeded in revoking Polish sovereignty over the largely Germanized Duchy of Prussia in 1660.

With the abdication of Emperor William II in 1918, Germany became a republic. During the interwar period, East Prussia and parts of West Prussia were exclaves of Germany, created as a result of the Treaty of Versailles when most of West Prussia and the former Prussian Province of Posen were ceded to Poland to create the Polish Corridor and the Free City of Danzig.

In 1920 plebiscites in eastern West Prussia and southern East Prussia were held under Allied supervision to determine if the areas should join the Second Polish Republic or remain in Prussia within the new Weimar Republic; 96.7% of the people voted for remaining within Germany, although a significant minority was of Polish language.

The Memel Territory, a League of Nations mandate since 1920, was occupied by Lithuania in 1923 without giving the inhabitants a choice on the ballot.

Shortly after the end of the war in May 1945, some Germans who had fled in early 1945 tried to return to their homes in East Prussia. However, they were stopped. The remaining German population of East Prussia was almost completely expelled by the Communist regime. During the war and shortly thereafter, many people were also deported as forced labourers to eastern parts of the Soviet Union, including the Gulag camp system. German place names were changed to either Russian or Polish names.

In April 1946, northern East Prussia became an official province of the Russian SFSR, with the Memel Territory becoming part of the Lithuanian SSR. In July of that year, the historic city of Königsberg was renamed Kaliningrad and the area named the Kaliningrad Oblast. After the expulsion of the German population, beginning in late 1947 ethnic Russians, Belarusians, and Ukrainians were settled in the northern part, and Polish expatriates from Polish lands annexed by the Soviet Union were settled in the southern part of East Prussia, now the Polish Warmian-Masurian Voivodeship.


In the Soviet part of the region, a policy of eliminating all remnants of German history was pursued. In 1967 this resulted in the demolition of the remains of Königsberg Castle by order of Leonid Brezhnev to make way on the site for the new "House of Soviets". Equally anti-German was the policy of communist Poland after the war, as German names were systematically removed, church yards and grave stones were ploughed under or demolished, houses were stripped of elements reflecting their German history, culture and language, and a policy was made which punished even the unofficial use of the German language by linguistically Slavic Masurian inhabitants, even though some continue to identify themselves with Germany and are able to speak fluent German, especially elderly inhabitants.

Since the fall of Communism in 1991, some German groups, among them also nationalists from the West have tried to help settle Volga Germans from eastern parts of Russia in the Kaliningrad Oblast. This initiative was only a small success, however, as most impoverished Volga Germans preferred to immigrate to the richer Federal Republic of Germany, where they could become German citizens through the right of return.

Although the 1945-1949 expulsion of Germans from the northern part of former East Prussia often was conducted in a violent and aggressive way by Soviet officials seeking revenge for Nazi crimes in the Soviet Union, the present Russian inhabitants of the Kaliningrad Oblast have much less animosity towards Germans. German names have been revived in commercial Russian trade and there is sometimes talk of reverting Kaliningrad's name back to the original name of Königsberg. Because the exclave during Soviet times was a military zone which nobody was allowed to enter without special permission, many old German villages are still intact, though they have become dilapidated over the course of time. The city centre of Kaliningrad, however, was completely rebuilt, as British bombs (1944) and the Soviet siege (1945) had left it in ruins.

The parts annexed by Poland are still heavily guarded by the central Polish government against reinstating any of the German heritage and history. Until 1990 Polish activists took measures to demolish churches, graveyards and road signs bearing indications to a German history or which were in German entirely. This Polish-Slavic nationalistic approach towards the "Recovered Territory" of southern East Prussia remains vivid even today, with old, German expellees trying to erect expulsion commemoration monuments. Except for the supported of the Roman Catholic Polish Archbishop of Warmia (Ermland), Dr. Edmund Piszcz, most Polish authorities are openly reluctant to recognise southern East Prussia's long German history and cultural heritage.