divisions with six or seven tank brigades and several independent tank platoons as support, totalling 600,000 soldiers. On 1 February, the Red Army began a large offensive, firing 300,000 shells into the Finnish line in the first 24 hours of the bombardment. Soviet offensive on the Karelian Isthmus Although the Karelian Isthmus front was less active in January than in December, the Soviets increased bombardments, wearing down the defenders and softening their fortifications. During daylight hours, the Finns took shelter inside their fortifications from the bombardments and repaired damage during the night. The situation led quickly to war exhaustion among the Finns, who lost over 3,000 soldiers in trench warfare. The Soviets also made occasional small infantry assaults with one or two companies. Because of the shortage of ammunition, Finnish artillery emplacements were under orders to fire only against directly threatening ground attacks. On 1 February, the Soviets further escalated their artillery and air bombardments. Although the Soviets refined their tactics and morale improved, the generals were still willing to accept massive losses 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 constant artillery barrage, the Soviets achieved a breakthrough on the Western Karelian Isthmus in the Second Battle of Summa. By 11 February, the Soviets had approximately 460,000 soldiers, 3,350 artillery pieces, 3,000 tanks and 1,300 aircraft deployed on the Karelian Isthmus. The Red Army was constantly receiving new recruits after the breakthrough. Opposing them, the Finns had eight divisions, totalling about 150,000 soldiers. One by one, the defenders' strongholds crumbled under the Soviet attacks and the Finns were forced to retreat. On 15 February, Mannerheim authorised a general retreat of the II Corps to a fallback line of defence. On the eastern side of the isthmus, the Finns continued to resist Soviet assaults, achieving a stalemate in the battle of Taipale. Peace negotiations Although the Finns attempted to re-open negotiations with Moscow by every means during the war, the Soviets did not respond. In early January, Finnish communist Hella Wuolijoki contacted the Finnish Government. She offered to contact Moscow through the Soviet Union's ambassador to Sweden, Alexandra Kollontai. Wuolijoki departed for Stockholm and met Kollontai