Editing Winter War (section)

===Battles of the Mannerheim Line===
The terrain on the Karelian Isthmus did not allow guerrilla tactics, so the Finns were forced to resort to the more conventional Mannerheim Line, with its flanks protected by large bodies of water. Soviet propaganda claimed that it was as strong as or even stronger than the [[Maginot Line]]. Finnish historians, for their part, have belittled the line's strength, insisting that it was mostly conventional trenches and log-covered [[Dugout (military)|dugouts]].<ref name="Trotter_62-63">[[#Trotter2002|Trotter (2002)]], pp. 62–63</ref> The Finns had built 221 strong-points along the Karelian Isthmus, mostly in the early 1920s. Many were extended in the late 1930s. Despite these defensive preparations, even the most fortified section of the Mannerheim Line had only one [[reinforced concrete|reinforced-concrete]] bunker per kilometre. Overall, the line was weaker than similar lines in mainland Europe.<ref name="Vuore1999_494-495">[[#Vuore1999|Vuorenmaa (1999)]], pp. 494–495</ref> According to the Finns, the real strength of the line was the "stubborn defenders with a lot of ''[[sisu]]''" – a Finnish idiom roughly translated as "[[Courage|guts, fighting spirit]]".<ref name="Trotter_62-63" />

On the eastern side of the Isthmus, the Red Army attempted to break through the Mannerheim Line at the battle of Taipale. On the western side, Soviet units faced the Finnish line at Summa, near the city of Viipuri, on 16 December. The Finns had built 41 reinforced-concrete bunkers in the Summa area, making the defensive line in this area stronger than anywhere else on the Karelian Isthmus. Because of a mistake in planning, the nearby Munasuo swamp had a {{convert|1|km|mi|adj=on}}-wide gap in the line.<ref name="Laaks1999_407">[[#Laaksonen1999|Laaksonen (1999)]], p. 407</ref> During the [[battle of Summa|First Battle of Summa]], a number of Soviet tanks broke through the thin line on 19 December, but the Soviets could not benefit from the situation because of insufficient co-operation between branches of service. The Finns remained in their trenches, allowing the Soviet tanks to move freely behind the Finnish line, as the Finns had no proper anti-tank weapons. The Finns succeeded in repelling the main Soviet assault. The tanks, stranded behind enemy lines, attacked the strongpoints at random until they were eventually destroyed, 20 in all. By 22 December, the battle ended in a Finnish victory.<ref name="Laaks1999_411-412">[[#Laaksonen1999|Laaksonen (1999)]], pp. 411–412</ref>

The Soviet advance was stopped at the Mannerheim Line. Red Army troops suffered from poor morale and a shortage of supplies, eventually refusing to participate in more [[Human wave attack|suicidal frontal attacks]]. The Finns, led by General [[Harald Öhquist]], decided to launch a counter-attack and encircle three Soviet divisions into a ''motti'' near Viipuri on 23 December. Öhquist's plan was bold; however it failed. The Finns lost 1,300 men, and the Soviets were later estimated to have lost a similar number.<ref name="Trotter_87-89">[[#Trotter2002|Trotter (2002)]], pp. 87–89</ref>