The Wehrmacht had entrenched itself within the tunnels of the underground system. Hours before fighting ended in Berlin on May 2, 1945, troops of the SS detonated explosives inside the north-south S-Bahn tunnel under the Landwehr Canal to slow the advance of the Red Army towards Berlin's city center. The entire tunnel flooded, as well as large sections of the U-Bahn network via connecting passages at the Friedrichstraße underground station. Many of those seeking shelter in the tunnels were killed. Of the then 63.3 kilometers of subway tunnel, around 19.8 kilometers were flooded with more than one million cubic meters of water.