This was the German evacuation of forces from Estonia as a result of the Soviet 'Tartu Offensive Operation' (17/25 September 1944).
The German forces involved were General Johannes Friessner’s Armeeabteilung 'Narwa' and General Ehrenfried-Oskar Boege’s 18th Army of Generalfeldmarschall Friedrich Schörner’s Heeresgruppe 'Nord', which were compelled to fall back by the offensive of General Ivan I. Maslennikov’s 3rd Baltic Front on the left through the German defences of the 'Valga-Linie', and of General Leonid A. Govorov’s Leningrad Front on the right over the lower reaches of the Narew river.
The Soviet objective in the 'Tartu Offensive Operation', which pitted 272,800 Soviet troops against 65,000 German and allied troops including numbers of Estonian conscripts and volunteers, poorly trained and badly equipped but determined to prevent a renewed Soviet annexation of their country, was the defeat and if possible the destruction of the 18th Army and the capture of Tartu within the Soviet intent to occupy all of Estonia with great rapidity. The way was paved for the Soviet offensive by the success of the Leningrad Front in driving Heeresgruppe 'Nord' back west of Lake Peipus and launching a series of operations around Narva. The Stavka planned that its forces would reach the Gulf of Riga and thus also trap the Armeeabteilung 'Narwa'. However, SS-Brigadeführer und Generalmajor der Waffen-SS Jürgen Wagner’s Kampfgruppe 'Wagner' was able to stabilise the front at the Emajõgi river, and General Hans Gollnick’s XXVIII Corps (supported by Omakaitse [Estonian militia] elements) managed to check the Soviets at the Väike Emajõgi and Gauja rivers, thereby preventing the 3rd Baltic Front from cutting off the Armeeabteilung 'Narwa'.
The German high command decided that it was important to maintain control over the southern shore of the Gulf of Finland, which eased the situation in Finland and kept the Soviet Baltic Fleet blockaded at the eastern end of the gulf, and to maintain the German hold on the oil shale reserves and associated industry in Ida-Viru.
At the start of the 'Tartu Offensive Operation' on 10 August, the Soviets had an advantage of 4.3/1 in men, 14.8/1 in artillery and 4.1/1 in armour, and the first main thrust was directed at the Petseri area in the south of Estonia. On the first day General Leytenant Vladimir Z. Romanovsky’s 67th Army broke through the defences of Gollnick’s XXVIII Corps and captured the town of Võru on 13 August. The German corps was driven west to the banks of the Väike Emajõgi and Gauja rivers, where it gained the support of an Omakaitse battalion of Viljandi county.
While the defence prevented the 3rd Baltic Front from cutting off the retreat of the Armeeabteilung 'Narwa' from Estonia, there was open country in the direction of Tartu, the main city of south-eastern Estonia. Heeresgruppe 'Nord' created the Kampfgruppe 'Wagner' for the defence of the new line. Soviet armour nonetheless drove a wedge between the Kampfgruppe 'Wagner' and the XXVIII Corps as Wagner lacked a troop strength sufficient to halt the Soviets in front of Tartu.
On 16 August, a special group commanded by General Leytenant Aleksei A. Grechkin, deputy commander of the 3rd Baltic Front, launched an amphibious assault over Lake Peipus behind the German left flank, crushing the defence of the Omakaitse and establishing a bridgehead in Mehikoorma, but then in fierce fighting a regiment of Estonian border guards stopped the Soviet advance. On 23 August, the 3rd Baltic Front launched an artillery bombardment of the positions held by the 2/45th SS Grenadierregiment 'Estland' (estnische Nr 1) covering the German right flank in the village of Nõo to the south-east of Tartu. The 282nd Division, 16th Tank Brigade, and two self-propelled artillery regiments bypassed the defence on the western side and captured the Kärevere bridge over the Emajõgi river to the west of Tartu: this was vitally important as it was one of only four bridges across the marshy flood plain, 60 miles (100 km) long, of the Emajõgi river. As a result of an error by German sappers, the bridge had not been blown.
SS-Sturmbannführer Léon Joseph Marie Ignace Degrelle improvised a defence line using his 5th SS Sturmbrigade 'Wallonien', thereby preventing a Soviet breakthrough to Tartu. A heavy German tank assault had been planned to attack behind the western flank of the Soviet line in Elva on 24 August. On the night before the attack, the designated commander of the operation SS-Brigadeführer und Generalmajor der Waffen-SS Hyazinth Graf Strachwitz von Gross-Zauche und Camminetz, was involved in a serious car accident and, without effective leadership, the German attack was defeated on the following day.
Four Soviet divisions launched an attack on Tartu with powerful armour and artillery support. After fierce street fighting, the Soviets took the city and established a bridgehead on the northern bank of the Emajõgi river on 25 August. As the Kampfgruppe 'Wagner' could not halt the Soviet offensive, Heeresgruppe 'Nord' passed control of the Emajõgi front to General Wilhelm Hasse’s II Corps. At the end of August the 3/45th SS Grenadierregiment (estnische Nr 1) was formed out of the Finnish 1/200th Regiment recently arrived in Estonia. Supported by the Estonian 37th and 38th Police Battalions and Oberst Mauritz Freiherr von Strachwitz’s tank unit, by 30 August it had destroyed the bridgehead of two Soviet divisions and recaptured Kärevere bridge. The operation shifted the entire front back to the southern bank of the Emajõgi and encouraged the II Corps to attempt the recapture of Tartu.
The attack of 4/6 September reached the northern outskirts of the city but was there halted and driven back by elements of the 86th, 128th, 291st and 321st Divisions. A comparative calm now descended on the front for 13 days.
Beginning on 17 September, a German naval force under Vizeadmiral Theodor Burchardi’s Admiral Östliche Ostsee command began evacuating elements of the German formations and Estonian civilians in an undertaking that, within six days, removed about 50,000 troops, 20,000 civilians and 1,000 prisoners. The remaining elements of Heeresgruppe 'Nord' in Estonia were ordered to withdraw into Latvia by way of Pärnu. General Hermann Breith’s III Panzerkorps reached the town by 20 September, while General Wilhelm Hasse’s II Corps retreated south to form the 18th Army's rearguard. As the Germans retreated the Soviet forces advanced, taking Tallinn on 22 September.
By 24 September the Soviet forces had demolished the harbour at Haapsalu, the Germans then evacuating Vormsi island, just off the coast, on the following day.