The 'Battle of Vyborg Bay' was fought between Soviet and Finnish forces, the latter with German support, during the 'Vyborg-Petrozavodsk Offensive Operation' (30 June/10 July 1944).

The Soviet 'Vyborg-Petrozavodsk Offensive Operation' against the Finns started on 10 June and managed to break through the Finnish defensive lines at Valkeasaari and Kuuterselkä on 15 June. This forced the Finnish forces on the Karelian Isthmus to withdraw to the defences of the still-incomplete 'VKT-linja'. Although Soviet advance captured Viipuri (Russian Vyborg) on 20 June, the main offensive got stuck in the stubborn Finnish defence of the Tali-Ihantala region. Despite heavy fighting and use of fresh reserves, the 'VKT-linja' bent but did not break, forcing the forces of the Leningrad Front to seek alternate routes past the Finnish defences. The Leningrad Front followed roughly the same plan as it had in the 'Talvisota' winter war of 1939/40 and made plans for an amphibious assault across Vyborg Bay.

Soviet forces committed in this battle were part of the Leningrad Front under the command of Marshal Leonid A. Govorov, who assigned to the attack across the Vyborg Bay to General Leytenant Ivan T. Korovnikov’s 59^th Army, to which the XLIII Corps was subordinated. Infantry forces involved in the offensive were the 124^th Division and 224^th Division, with the 80^th Division in reserve. Only a few Soviet tanks were assigned to support the offensive. Several artillery regiments were also assigned to the offensive, which also had air support and light naval forces of Vitse Admiral Vladimir F. Tributs’s Baltic Fleet as well as the 260^th Naval Regiment,

Initially, the forces responsible for the defence were the 22^nd Rannikon Tykistörykmentti (coastal artillery regiment) of the Eastern Bay of Finland Coastal Brigade under the command of the Finnish navy, and parts of Eversti Lars Melander’s (from 17 June Eversti Urho Tähtinen’s Ratsuväkiprikaati (cavalry brigade) under Kenraalimajuri Antero Svensson’s V Armeijakunta. Both the 22^nd Rannikon Tykistörykmentti and nt and Generalmajor Hero Breusing’s newly arrived German 122^nd Division were subsequently subordinated to the V Armeijakunta. A large portion of the Finnish navy supported the defensive operations.

Initially the islands of Vyborg Bay were in a moderately strong position, with the Finnish garrison on the Koivisto islands preventing Soviet naval forces from gaining access to the bay. The Baltic Fleet landed a small assault force on the islands, but the Finns managed to keep the beach-heads contained. Nevertheless, Finnish headquarters decided it would be impossible to maintain the necessary flow of supplies to the troops in the islands in the fact of Soviet air supremacy, and withdrew their forces from the islands unopposed. This opened the route for the Baltic Fleet to get safely into Vyborg Bay.

The fighting in Vyborg Bay started on 30 June, when the Soviet 224^th Division’s attempt to seize the islands of Teikari and Melansaari. The Finnish forces on the islands drove the attackers back, inflicting heavy losses on the Soviet troops. Renewed Soviet attacks on 4 July met success in the islands near Uuras, but the attempt to land on Teikari was again repulsed with heavy Soviet losses.

On 4 and 5 July the Finnish navy, supported by several German Artilleriefährprahme gun barges, made several raids on Vyborg Bay in an attempt to disrupt the Soviet landings on the islands. Heavy Soviet resistance from shore-based artillery, numerous motor torpedo boats and the Soviet air forces compelled the Finns to withdraw without reaching their intended target area. Although none of the Finnish vessels and craft was sunk, most of them suffered casualties among their crews and were also badly damaged, requiring immediate repair. This situation effectively forced the Finnish naval forces to withdraw from the battle. Of the Finnish vessels, the worst damage was suffered by the auxiliary gunboat Viena during a Soviet air attack while it was at anchor. The vessel nearly sank but was nonetheless able to return to Helsinki for repair.

Parts of the Soviet 124^th Division captured the islands of Teikari and Melansaari on 5 and 6 July. Fighting on the other islands closer to the northern shore continued until 8 July, when the Soviet 124^th and 224^th Divisions attempted landings on the bay’s northern coast. The defending 122^nd Division repulsed the attempts, and the Soviet 59^th Army switched to defence after these attempts, and fighting in the bay came to an end.

In costly battles the 124^th and 224^th Divisions had managed to capture the islands dominating Vyborg Bay, but failed to gain a beach-head on the northern shore of the bay. With both the initial attempt at Tali-Ihantala and the crossing at Vyborg Bay blocked, the Leningrad Front turned its attention to the still undecided battles raging in the area of Äyräpää and Vuosalmi.