Mazovia had become Poland's fief in 1351 after the reunification of the Polish state by Władysław I in the early fourteenth century.

The eastern part of the Mazovia region (Łomża) had been settled in the fifteenth century, mainly by the yeomanry (drobna szlachta).

Western Mazovia had in the second half of the fifteenth century been incorporated into the Polish state, as, in 1526/1529, is the main part, with its capital in Warsaw.

In comparison with Greater Poland and Lesser Poland, Mazovia, with the lowest urban population, is considered underdeveloped.