The Old Prussians (German: Pruzzen or Prußen; Latin: Pruteni; Latvian: Prūši; Lithuanian: Prūsai; Polish: Prusowie) were a set of Baltic tribes that lived in East Prussia and neighbouring parts of Lithuania and Poland. They were closely related to the Lithuanians. They spoke a Baltic language known as Old Prussian, the most archaic of the Baltic languages and followed the pagan Prussian mythology.
There is patchy nomicultural indications that the pre-Baltic settlers in East Prussia generally named their settlements after the local streams, lakes, seas, or forests by which they settled. The subsequent clans and tribal then took the name of the place they had settled in. For example, the name "Barta", is "the home of the Barti" and is related to the name of the Bartis River in Lithuania.
The various tribal names of the Prussian tribes apparently reflected the theme of the local landscape and were based on a respect for water, a logical theme since the land is dotted with thousands of lakes, streams, and swamps (now called Masurian Lake District). To the south, the terrain runs into the Pripet Marshes at the headwaters of the Dnieper River; these have been an effective barrier over the millennia. This difficult to navigate landscape and the Lithuania/Old Prussian fighting spirit helped preserve the Baltic language group as the most ancient in Europe.
Since first appearance in the area of Polish dukes Mieszko and Boleslaw, who attempted conquest of Prussian lands, repeated take-over- attempts followed and were repelled. Prussians successful defense however became increasingly more difficult when Poland's Konrad I, Duke of Masovia called for Papal Crusades, and then appealed to the Knights to defend his borders and subdue the neighboring pagan Baltic Prussians in 1226. He allowing the eutonic Knights use of Chełmno Land (Culmerland) as a base for their campaign. This being a time of widespread crusading fervor throughout Western Europe, Hermann von Salza considered Prussia a good training ground for his knights for the wars against the Muslims in the Middle East's Outremer. With the Imperial Golden Bull of Rimini edict, Emperor Frederick II bestowed on the Order a special imperial privilege for the conquest and possession of Prussia, including Culmerland, verified with the Papal Golden Bull of Rieti. The Teutonic Order came under authority of the Archbishopric of Riga in Livonia.
In 1235 the Teutonic Knights assimilated the smaller Order of Dobrin ( Dobrzyń), which had been established earlier by Christian, the first Bishop of Prussia. The bloody conquest of Prussia was accomplished in over more than 50 years. The native Prussians who remained unbaptised and wished to remain in their own nature beliefs were either subjugated, killed, or exiled to Lithuania and Russian tribal territories.
The fighting between the Knights and the Old Prussians was horrific as the chronicles of the Order state the Prussians would"roast captured brethren alive in their armour, like chestnuts, before the shrine of a local god".
The Papal Order of Teutonic Knights then began to direct their campaigns against pagan Lithuania, especially after 1291, who had a similar Lithuanian mythology. Other campaigns would hit parts of Poland, southern Finland and the Republic of Novgorod.
With the Protestant Reformation parts of the land of the Old Prussians became Prussian (German) Province of East Prussia.
With Counter Reformation Lutherans from Lithuania and Poland and other countries took refuge in Lutheran Protestant Prussia and Lithuanian-speaking Prussians were concentrated in the northeast East Prussia (Lithuania Minor). Before and during Christianization Germanic people sought refuge in not yet christianized territories. With the Papal Teutonic Knights invasions in the region in the 13th century and over time the Baltic Old Prussian ethnic group became completely Germanized and the Old Prussian language died out during the 18th century, while parts of the language remained in family names, place names and the East-Prussian language.
Lithuanian proper still lingered on until World war 2 in the Klaipėda Region, but later gained much ground after the region's annexation by the Russian (RSFR) lead USSR
The People were of similar Baltic origin as the Latvians and Lithuanians, but the language is extinct. DNA Haplogroup testing has recently shown evidence of some Baltic people still living in the former territory around the Warmian-Masurian Voivodeship, but they are probably decedents of Cold War immigrants, anti-Bolshevik exiles and World War II refugees from Latvia and Lithuania.Memel- Klaipėda Region is now inhabited mostly by Lithuanians.