 The terrain on the Karelian Isthmus did not allow the exercise of guerilla tactics , so the Finns were forced to resort to the more conventional Mannerheim Line , with its flanks protected by large bodies of water . Soviet propaganda claimed that it was as strong as or even stronger than the Maginot Line . Finnish historians , for their part , have belittled the line 's strength , insisting that it was mostly conventional trenches and log @-@ covered dugouts . 
