The '2nd Battle of Summa' was fought near the village of Summa (now Soldatskoye), on the main road linking Leningrad and Viipuri, between Soviet and Finnish forces as the second of a two-phase battle within the 'Winter War' (1/15 February 1940).
As the Soviets had found it too difficult to breach the Finnish defensive line in the Summa sector in the '1st Battle of Summa', they then attacked 6.2 miles (10 km) father to the east in the Lähde sector between the Summajärvi lake in the west and the Munasuo swamp in the east. If the Soviet forces broke through in this sector, they would be in a position to outflank and possibly encircle the Finnish 3rd Division holding the Summa position. Komandarm 1-ranga Semyon K. Timoshenko, the commander-in-chief of the North-West Front, knew that he could beat the Finns in a battle of attrition. Thus Timoshenko’s plan was to wear down the Finnish forces in a sustained assault and then launch a high-intensity final attack.
From 1 February, the Soviets launched a series of large probing actions against the Finnish lines, and for more than 10 days the Finns held their line at every position. On 11 February, however, the Soviets began their major assault, and on 12 February, a minor breach in the Finnish lines in the Lähde sector led to a Finish disaster. By that time, the Soviet forces had driven so many breaches into the 'Mannerheim-linja' defences that the reports concerning them were virtually disregarded. It was intended that on the following morning, a Finnish counterattack was to be launched by the entire 5th Divisioona (division), the only reserve in easy reach of the front line, but only one of its three regiments was available as the other two had perforce been despatched elsewhere.
Thus only two Finnish battalions launched a counterattack against the well-equipped Soviet 245th Regiment and 255th Regiment, which were supported by effective artillery and 35th Tank Brigade. The Finnish attack was thrown back with heavy casualties, and the Soviets then made efforts to exploit this initial success. One of the Soviet tank regiments advanced as far as the Lähde road junction but then halted despite the fact that a more complete victory would then have been in the Soviets' grasp.
Many Finnish companies had been reduced to half their original strength: one company lost 86 out of 110 men. During the night pf 14/15 February, the Finns began withdrawing from the Summa position, and during the morning of 15 February the Soviets attacked an empty position at Summa with more than 100 tanks and two divisions. That afternoon, Sotamarsalkka C. G. E. Mannerheim, the Finnish commander-in-chief, ordered a general retreat to the so-called Intermediate Line.