The next five days saw very heavy fighting as the Soviets slowly advanced through heavy German defences and repelled German counterattacks. On 13 January, bad weather prevented the Soviet side from employing their air force. That day they gained almost no ground and incurred heavy losses. The German side, after their counterattacks had failed to throw back the Soviet troops, started further reinforcing the area by assembling battle groups using portions of divisions from the quiet parts of the front. These included battle groups from the 1st Infantry Division, the 61st Infantry Division, the 5th Mountain Division and the SS Police Division.