 In addition to its navy , Finland had coastal artillery batteries to defend important harbors and naval bases along its coast . Most batteries were left over from the Imperial Russian period , with 152 mm ( 6 @.@ 0 in ) guns being the most numerous . However , Finland attempted to modernize its old guns and installed a number of new batteries , the largest of which featured a 305 mm ( 12 @.@ 0 in ) gun battery originally intended to block the Gulf of Finland to Soviet ships with the help of batteries on the Estonian side . 
