The Vyborg–Petrozavodsk offensive or Karelian offensive was a strategic operation by the Soviet Leningrad and Karelian Fronts against Finland on the Karelian Isthmus and East Karelia fronts of the Continuation War, on the Eastern Front of World War II. The Soviet forces captured East Karelia and Vyborg/Viipuri. After that, however, the fighting reached a stalemate.
The operations of the strategic offensive can be divided into the following offensives: Viipuri (10–20 June) by the Leningrad Front Virojoki-Lappeenranta (21 June – 15 July) by the Leningrad Front Koivisto landing (20–25 June) by the Baltic Fleet Svir–Petrozavodsk (21 June – 9 August) by the Karelian Front Tuloksa landing (23–27 June) by the Soviet Ladoga Flotilla
Background In January 1944, Soviet forces raised the Siege of Leningrad and drove the German Army Group North back to the Narva-Lake Ilmen-Pskov line. Finland had conducted peace negotiations intermittently during 1943–1944 with the Western Allies and the USSR, but no agreement had been reached. Finland asked for peace conditions again in February, but the Finnish Parliament (Eduskunta) considered the terms received impossible to fulfill. After Finland had rejected these peace conditions, and Germany halted the Soviet advance,Newton (1995) the Stavka (Main Command of the Armed Forces of the Soviet Union) started to prepare for an offensive to force Finland's exit from the war.Gilbert, p. 536"
The plan In order to destroy the Finnish Army and to push Finland out of the war, the Stavka decided to conduct the Vyborg–Petrozavodsk offensive. The strategy called for a two-pronged offensive, one from Leningrad via Vyborg to the Kymi river, and the second across the Svir River through Petrozavodsk and Sortavala past the 1940 border, preparing for an advance deep into Finland.Platonov (1964) The plan called for the Finnish army to be destroyed on the Karelian Isthmus, and the remains blocked against the western shore of Lake Ladoga between the two assaults and Lake Saimaa.Zolotarev (1999), pp. 97–98 Ministry of Defence of the Russian Federation. Наступление советских войск на Карельском перешейке и в Южной Карелии По замыслу Ставки войска Ленинградского и Карельского фронтов при содействии Краснознаменного Балтийского флота, Ладожской и Онежской военных флотилий мощными ударами должны были разгромить противостоящего противника, овладеть Выборгом, Петрозаводском и выйти на рубеж Тикшеозеро, Сортавала, Котка. Операцию начинали войска Ленинградского фронта, затем в наступление переходил Карельский фронт.
The main strategic objectives of the offensive were to push Finnish forces away from the north of Leningrad, to drive Finland out of the war,Glantz (2002), pp. 443, 458 and to create better conditions for a major offensive to the south against Germany.Gebhardt (1989), p. 2Glantz (1998), pp. 201–03Erickson (1993), pp. 329–30Moisala (1988)
The Finnish army had been preparing defensive fortifications since 1940, and three lines of defense on the Karelian Isthmus. The first two were the "Main line", which was constructed along the frontline of 1941, and the VT-line (Vammelsuu-Taipale) running 20 km behind the main line. These lines were reinforced with numerous concrete fortifications, but the work was still ongoing. The third line, the VKT-line (Viipuri-Kuparsaari-Taipale) was still on the drawing board and the construction of the fortifications began in late May 1944 at the Vyborg sector of the line. At the northern bank of the Svir River () the Finnish army had prepared a defence in depth area which was fortified with strong-points with concrete pillboxes, barbed wire, obstacles and trenches. After the Winter War, the Salpa Line was built behind the 1940 border with concrete bunkers in front of the Kymi river.
To overcome these obstacles, the Stavka assigned 11 divisions and 9 tank and assault gun regiments to the Leningrad Front. That meant that there were 19 divisions, 2 division strength fortified regions, 2 tank brigades, 14 tank and assault gun regiments at the Isthmus, all of which included over 220 artillery and rocket launcher batteries (almost 3,000 guns/launchers). Around 1,500 planes from the 13th Air Army and the Baltic Fleet naval aviation also contributed to the operation which included surface and naval infantry units of the Baltic Fleet.
To the east of Karelia, the Stavka planned to use 9 divisions, 2 sapper brigades, 2 tank brigades and 3 assault gun regiments, raising the whole strength to 16 divisions, 2 fortified regions, 5 separate rifle brigades, 2 tank brigades, 3 assault gun regiments and 3 tank battalions. They were supported by Lake Ladoga and Lake Onega naval flotillas and the 7th Air Army.
Vyborg-Vuoksi offensive At the Karelian Isthmus front there were on average 120 Red Army artillery pieces for every kilometer of frontline, with up to 220 artillery pieces per kilometer on the breakthrough sector at Valkeasaari. In addition to heavy coastal artillery of the Leningrad area and the guns of the capital ships of the Baltic Fleet (Oktyabrskaya Revolutsiya, , ) the Stavka had also assigned heavy siege artillery (280 to 305 mm) in support of the attack.
On June 9, a day before the main Soviet offensive, the 1,600-strong 13th Air Army conducted a major aerial assault. At the same time, artillery units of the Leningrad Front and the Baltic Fleet shelled Finnish positions for 10 hours. The Finnish Army was in a well-fortified position, but the Soviet air attacks surprised the defending Finnish army and undermined its resistance causing many Finnish units to retreat and suffer from thousands of desertions.Bergstrom (2008)
Valkeasaari On June 10, the Soviet 21st Army, spearheaded by 30th Guards Corps, opened the offensive on the Valkeasaari sector, which was defended by 1st Infantry Regiment of Finnish 10th Division. During the day, the Soviet units captured frontline trenches and destroyed fortifications, shattering the first Finnish defense line at the breakthrough sector.
Kuuterselkä On June 13, the Soviet 21st Army's offensive reached the partially completed VT-line. The defensive position was breached at Kuuterselkä by June 15. Though the line was breached, the Finnish resistance managed to delay further Soviet advances.
Siiranmäki Simultaneous to Kuuterselkä, the Soviet 23rd Army attempted to break through at a perceived weak point in the Finnish VT-line at Siiranmäki. Siiranmäki was the first place where Finnish troops were able to use anti-tank Panzerfausts and Panzerschrecks which were imported from Germany. Though Finnish troops managed to contain the Soviet breakthrough at Siiranmäki, the VT-line had already been breached at Kuuterselkä. Soviet 98th Infantry Corps fighting in Siiranmäki against Finnish 7th Regiment announced to have lost during period of June 13 to June 16: 3 784 soldiers including 887 killed in action based on their own report. Red Army and especially Guard units took heavy losses in Siiranmäki-Kuuterselkä with 20,000 KIA, MIA or WIA.
Vyborg The Finnish army attempted to buy time by engaging in delaying actions during its retreat so that additional forces from East Karelia would be able to reach the front, and the VKT-line could be prepared for combat. However, on June 19 forces of the first Leningrad Front had reached Vyborg, and the first phase of the offensive was completed by the capture of the city on June 20, when the defending Finnish 20th Infantry Brigade fled in panic. Though Leningrad Front had managed to capture Vyborg within the time table set by the Stavka they had been unable to prevent retreating Finnish units from regrouping and fortifying on the VKT-line. Unlike many battles on the Eastern Front in the Karelian Isthmus the Red Army was unable to trap any large Finnish units – not even a single battalion. Finnish forces had managed to retreat. At the same time more and more Finnish reserves were arriving at the VKT-defense line, where terrain was much more favorable for defenders than for the armored Red Army units. The Soviet 21st Army also faced logistics issues after its fast 120 km advance to west.
Virojoki–Lappeenranta offensive
Mannerheim had asked for German help, and on June 17 Gefechtsverband Kuhlmey arrived in Finland, followed on June 21 by the 303rd Assault Gun Brigade (at half strength) and the 122nd Infantry Division. Also, new German anti-tank weapons, Panzerfausts and Panzerschrecks, were issued to Finnish army troops. Late on June 21, German foreign minister von Ribbentrop arrived to Finland in an attempt to extract political concessions from the military help.
On June 21, the Stavka ordered continued attacks on the Imatra–Lappeenranta–Virojoki defence line, on the Salpa Line sector of the front. Another group would attack northwards to Käkisalmi (now Priozersk, Russia) and surround the Finns defending the eastern VKT-line while preparations would be made for an advance towards Kotka, Kouvola and the Kymi river.