 Soviet 1944 offensive had started on June 10, 1944 and in matter of days broke through of the fortified Finnish defense lines in southern Karelian Isthmus.On June 20 the advancing Soviet forces were already literally on the gates of Viipuri.Finnish 20th Brigade had been transferred to defend the city however it had been inadequately supplied and lacked effective anti-tank weapons as it had neither 7.5 cm Pak 40 anti-tank guns nor knowledge on how to use the few available Panzerfaust or Panzerschreck anti-tank weapons.