 Although the Soviets refined their tactics and morale improved , the generals were still willing to accept massive losses in order to reach their objectives . Attacks were screened by smoke , heavy artillery , and armour support , but the infantry charged in the open and in dense formations . Unlike their tactics in December , Soviet tanks advanced in smaller numbers . The Finns could not easily eliminate tanks if infantry troops protected them . After 10 days of round @-@ the @-@ clock artillery barrages , the Soviets achieved a breakthrough on the western Karelian Isthmus in the second battle of Summa . 
