English: Position of barricades during the Warsaw Uprising on a pre-war map of Warsaw (1935). Such barricades were erected in all of the Polish-held territory from the very beginning of the struggle. Initially they were constructed by local civilian population, but soon the Armia Krajowa headquarters dispatched units composed of engineers (many of whom were university professors) to supervise the construction. The barricades were built from a variety of materials, from pieces of furniture strengthened with pavement bricks, to streetcars, to broken trucks and rubble. Several baricades were strengthened with captured German tanks. Warsaw University of Technology area in which heavy fights occurred during all of the Uprising are marked with letters PW, location of baricades marked in dark red.