Instead, the Soviets sent full divisions. On 11 December, the Finns rearranged the defence of Lapland and detached the Lapland Group from the North Finland Group. The group was placed under the command of Kurt Wallenius. In southern Lapland, near the village of Salla, the Soviet 88th and 122nd Divisions, totaling 35,000 men, advanced. In the Battle of Salla, the Soviets proceeded easily to Salla, where the road split. Further ahead was Kemijärvi, while the fork to Pelkosenniemi lead northwest. On 17 December, the Soviet northern group, comprising an infantry regiment, a battalion, and a company of tanks, was outflanked by a Finnish battalion. The 122nd retreated, abandoning much of its heavy equipment and vehicles. Following this success, the Finns shuttled reinforcements to the defensive line in front of Kemijärvi. The Soviets hammered the defensive line without success. The Finns counter-attacked, and the Soviets retreated to a new defensive line where they stayed for the rest of the war. To the north was Finland's only ice-free port in the Arctic, Petsamo. The Finns lacked the manpower to defend it fully, as the main front was distant at the Karelian Isthmus. In the battle of Petsamo, the Soviet 104th Division attacked the Finnish 104th Independent Cover Company. The Finns abandoned Petsamo and concentrated on delaying actions. The area was treeless, windy, and relatively low, offering little defensible terrain. The almost constant darkness and extreme temperatures of the Lapland winter benefited the Finns, who executed guerrilla attacks against Soviet supply lines and patrols. As a result, the Soviet movements were halted by the efforts of one-fifth as many Finns. Aerial warfare Soviet Air Force The USSR enjoyed air superiority throughout the war. The Soviet Air Force, supporting the Red Army's invasion with about 2,500 aircraft (the most common type being Tupolev SB), was not as effective as the Soviets might have hoped. The material damage by the bomb raids was slight as Finland offered few valuable targets for strategic bombing. For example, the city of Tampere was one of the most important targets because it was an important railway junction, and also housed State Aircraft Factory and the Tampere Linen and Iron Industry premises, which manufactured munitions and weapons, including grenade launchers. Often, targets were village depots with little value. The country had few modern highways in the interior, therefore making the railways the main targets for bombers. Rail tracks were cut