History of Mazury

Estimates range from about 170,000 to 220,000 Old Prussians living in the whole Prussia around 1200. The wilderness was their natural barrier against the attacks by would-be invaders. During the Northern Crusades of the early 13th century, the Old Prussians used this wide forest as a line of defence. They did it again against the Knights of the Teutonic Order invited to Poland by Konrad Mazowiecki in 1226. The order's goal was to convert the native population to Christianity and baptist it by force if necessary. In the subsequent conquest which lasted over 50 years, the original population was nearly exterminated especially during the major Prussian rebellion of 1261–83.

Teutonic Order

After the Order's acquisition of Prussia, Poles (or more specifically, Mazurs, that is inhabitants of the adjacent region of Mazovia) began to settle in the southeastern part of the conquered region. German, Dutch, Flemish, and Danish colonists entered the area afterward, from the northwest. The number of Polish settlers grew significantly again in the beginning of 15th century, especially after the first and the second treaties of Thorn, in 1411 and 1466 respectively, following the Thirteen Years' War and the final defeat of the order. Later assimilation of the German settlers as well as the Polish immigrants and native inhabitants created the new Prussian identity, although the sub regional difference between the German- and Slavic-speaking part remained. Western half of the province was ceded to Poland, and the grand master (still ruling, among others, also Masuria) became a vassal of the Polish crown.

Ducal Prussia

The secularization of the Teutonic