 The coastal artillery had a greater effect upon the land war by helping to reinforce the defence in conjunction with army artillery . Two sets of fortress artillery made significant contributions to the early battles on the Karelian Isthmus and in Ladoga Karelia . These were located at Kaarnajoki on the eastern isthmus and at Mantsi on the northeastern shore of Lake Ladoga . The fortress of Koivisto provided similar support from the southwestern coast of the isthmus . Coastal artillery had the ability to fire high @-@ explosive shells of 152 mm ( 6 @.@ 0 in ) calibre to a range of 25 km ( 13 nmi ; 16 mi ) . 
