Up to half a million civilians turned out to various points on the outskirts of the city to construct three fortified rings – the furthest, 70 miles west of the city, ran along the River Luga. Their efforts produced 650 miles of trenches, 430 miles of anti-tank ditches, over 5,000 concrete gun emplacements (or pillboxes), and 370 miles of barbed-wire entanglements.
