The 'Battle of Nietjärvi' was a Soviet and Finnish battle of the 'Jatkosota' continuation war (15/17 July 1944).

Nietjärvi is a village by the Nietjärvi lake of the Ladoga Karelia district to the north of Lake Ladoga in the south-western corner of the Aunus Karelia frontier, in an area which belonged to Finland up to the end of the continuation war. Here the Finnish 'Aunus' Ryhmä (Aunus group) was, on 11 July 1944, readied in the 'U-linja' defence line to hold in the event of the expected Soviet offensive. The construction of the 'U-linja' had been initiated seven months earlier on the line linking Nietjärvi, Lemetti and Loimola as the fortified line behind the 'PSS-linja' (Pisi, Saarimäki and Sammatus line), which was the most strongly fortified defence line in the Olonets Karelia region to the north and north-east of Lake Ladoga.

Up to June, the front line between the Soviet and Finnish forces in this area had extended in general along the line of the Svir river, which flows from Lake Onega to Lake Ladoga. Before the fighting started, the Finns had abandoned the bridgehead which they had occupied on the southern shore of the Svir river when the redeployment of troops to the Karelian isthmus made it impractical to hold this any longer. Behind the front line there was a secondary defensive line before the strong 'PSS-linja' for the Finnish army to slow any Soviet advance. The long-awaited Soviet 'Svir-Petrozavodsk Offensive Operation' began on 21 June in overwhelming strength and pushed through Finnish first-line defences. The Soviet offensive stalled at the 'PSS-linja', but a combined effort by the assaulting army forces and naval infantry landing behind the Finnish lines made the further retention of the 'PSS-linja' impossible for the Finns, who therefore started to withdraw toward the 'U-linja' while delaying Soviet advance.

During the previous three weeks, the Finnish defenders had managed to delay and distract the progress of the Soviet offensive, degrading and nibbling at the sharpest edge of the Soviet attack. The Finnish withdrawal came to an end on the 'U-linja' and, after establishing the location and strength of the Finnish defences, the Soviets began to launch local probing attacks against the 'U-linja' defences in an attempt to find possible weak spots suitable for a breakthrough attempt. The Soviet forces then decided to breach Finnish defences along the main coastal road at Nietjärvi and advance to Kittilä, for an advance to Kittilä would provide the Soviet forces with access to the better sections of the Finnish road network, as well as to several roads into the Finnish rear areas at Sortavala, Värtsilä and Matkaselkä.

At dawn on 15 July, Kenraalimajuri Kustaa Tapola’s [e[5^th Divisioona was deployed with the sector between Lake Ladoga and Nietjärvi held by Everstiluutnantti Elis Rytkönen’s 44^th Jalkaväkirykmentti (infantry regiment), and Eversti Heikki Saure’s 2^nd Jalkaväkirykmentti on the north-eastern side of Nietjärvi.

During the morning of 15 July, the artillery and mortars of General Leytenant Aleksei N. Krutikov’s 7^th Army opened a fierce fire preparations. The resulting dust, sand and smoke clouds severely reduced the visibility, making it difficult to see anything. After the artillery preparation, the 7^th Army began and infantry assault supported by armoured units. By 12.00, the Finnish defences had been able to stop the Soviet advance everywhere except on the western side of Nietjärvi, where the 1 and 2/44^th Jalkaväkirykmentti were unable to hold back the assault. The Soviets followed their initial success with another breakthrough attempt on the north-western shore of the Nietjärvi lake in Yrjölä. Lack of reserves made it difficult for the Finns to respond decisively to the Soviet assault, but by the evening the Finns had succeeded in halting the Soviet forces' breakthrough attempt on all but a 440-yard (400-m) wide section of the line, which the Soviets held. Throughout the evening the Soviet offensive continued relentlessly with potent tactical air support. The Finnish air force was also active in the battle by bombing Soviet formations on the south-eastern edge of the Nietjärvi lake. On 15 July, artillery battalions supporting [e[5^th Divisioona fired 10,170 rounds and the associated mortars 4,900 rounds.

The Finns' counterattack to regain the overrun sector of their defence line was launched in the morning of 16 July. The entire day was occupied by continuous and heavy fighting, and by the evening the Soviets held part of the village of Nietjärvi and part of the defence line (a stretch of interconnected trenches) on a low hill in the area. As frontal assault was deemed likely to be too expensive, so the Finns opted instead to isolate the Soviets by assaulting along the trenches with artillery used to prevent Soviet reinforcements from reaching the area. At 22.30 in the evening of 16 July, the Finnish artillery and mortars began a preparation which was immediately followed by an infantry assault along the trenches from the both ends with automatic rifles, hand grenades and flamethrowers.

In the early morning hours of 17 July, the Finnish units moving along the trench from both ends linked. Only a small number of Soviet troops trapped to the trench or beyond it escaped. The Soviet forces tried to support the troops fighting in the trench but the Finnish artillery prevented reinforcements from reaching the combat area.

The Soviets had thus been unable to penetrate the 5^th Divisioona's defences in the 'U-linja'. The heaviest Soviet losses were suffered by the 114^th Division, whose 762^nd Regiment was totally destroyed. The Finns captured a Soviet message to their headquarters reading 'The regiment destroyed, the flag saved.' The main bulk of the 114^th Division’s two other regiments were also very heavily mauled. Additionally, the 272^nd Division suffered heavy losses, and 40 Soviet tanks that had attacked in the direction of Nietjärvi were also lost. The breakthrough attempt had cost the Soviets more than 6,000 casualties, of which more than 2,000 were dead in this relatively short but very brutal battle. Not many Soviet soldiers were taken prisoner by the Finns.

The Finns suffered the loss of 500 men killed or missing, and 700 men wounded.

In the 'U-linja' fighting of 11 to 15 July, the Finnish artillery fired 54,300 rounds, a figure greater than that of any other battle during the summer of 1944, while mortars fired 24,400 rounds. Infantry battalions received the greatest level of artillery support. The Finnish fire using the element of surprise with very short half-minute or one-minute artillery barrages, and counter-battery fire was largely responsible for the decimation of the Soviet forces despite the absence of any significant support by the Finnish air force.

The highly efficient co-operation between the various elements of the Finnish armed forces had helped the 'Aunus' Ryhmä to stop the advance of General Kyrill A. Meretskov’s Karelian Front along the shores of Lake Ladoga at the 'U-linja'. The Finnish concentration of artillery and mortar fire once again played a vital role, as indeed it did in many other critical combat situations during summer of 1944. The Soviet 7^th Army’s attempt to get around of the 'U-linja' meant that engagements in the frontier region to the north of Lake Ladoga were smaller. The Soviet move to extend the front required the Finns to extend their line, a fact which set the stage for the 'Battle of Ilomantsi' fought farther to the north. The Finnish defence had prevented the Soviets from advancing from the northern side of Lake Ladoga into the larger battle on the Karelian isthmus: had the Soviets not been brought to a halt in the Lake Ladoga area, the Finnish forces fighting on the Karelian isthmus would have been caught between two Soviet armies on the narrow isthmus in the area limited by the Gulf of Finland in the south and Lake Ladoga in the north.