"Historic Podlasie stretched from north to south for some 30 miles, and was located between Mazovia and Rus principalities of Brzesc and Grodno (...) It was a sparsely populated province, covered by dense forests, with four major rivers: the Biebrza, the Narew, the Bug and the Krzna. Due to population growth in Mazovia and Rus, Podlasie became a settlement area - Mazovians settled near Tykocin, Rajgrod and Goniadz, while Ruthenians settled near Bielsk Podlaski. In northern districts of Podlasie, near Augustow, the Yotvingians resided (...) After the 1241 Mongol invasion of Poland, Podlasie turned into a desert, with population decimated by Asiatic hordes. Poles did not return here until the late 13th century, despite the fact that the province was already controlled by the Grand Duchy of Lithuania (...)