The Battle of Vilnius () or the Vilnius operation () took place in the autumn of 1915 between the cities of Vilnius and Daugavpils. It was strategic withdrawal by Russian forces on the Eastern Front of World War I, after a successful summer German offensive. The German armies were under the command of Supreme Commander of All German Forces in the East, Field Marshal Paul von Hindenburg. Although weakened by the transfer of 12 divisions to France and the Balkans, as part of taking a defense, Hindenburg had his forces conduct several secondary offensive operations. Half of the Russian forces and the main German forces on the Eastern Front took part in the battle. However, the numerical superiority of the Russians did not allow Hindenburg to achieve a lasting success. Further actions for the Germans were unsuccessful as they suffered losses without achieving their goal of taking Daugavpils.
Background The limited success of the Hindenburg's Army Group after the sieges of Kaunas and Novogeorgievsk forced the Chief of German Great General Staff, General of Infantry Erich von Falkenhayn, to make the final decision to curtail operations in the German Eastern front, especially since large regroupings of troops were necessary for the offensive against Serbia and strengthening the defense in France and Belgium. On August 27–28, 1915, Emperor Wilhelm II, at the insistence of Falkenhayn, issued a directive on the urgent construction of long-term defensive zones on the Eastern Front from the Baltic Sea in the area north of Mitava to the Narew river further to Kovel. At the same time, the army groups of Prince Leopold of Bavaria and August von Mackensen should continue the offensive solely with the aim of occupying positions more convenient for defense (bypassing from the north of Białowieża Forest), and the army group of Hindenburg - for "causing a major defeat to the enemy".
Significant changes have taken place in the management of the Russian army in the field. As early as August 17, the chief of staff of the Supreme Commander Nikolai Yanushkevich issued a decision on the division of the armies of the Northwestern Front despite the objections of the Commander-in-Chief Mikhail Alekseyev. On the night of August 31, the directorates of the Northern Front were formed; General of Infantry Nikolai Ruzsky was appointed commander-in-chief, Major General M. Bonch-Bruyevich was appointed his chief of staff; the front included the 6th, 5th and 12th Armies - the management of the latter was transformed from the apparatus of the 13th Army. The task of the armies of the Northern Front was to cover the routes to Petrograd, including from the Baltic coast. The task of the armies of the Western Front (Commander-in-Chief Infantry General Alekseyev, Chief of Staff Lieutenant General ) was the defense of the Vilnius, Grodno-Bialystok and Brest-Pinsk regions. The position of the armies of the Eastern Front was complicated by the fact that the Germans stood on the outskirts of Vilnius and had already captured Brest-Litovsk.
Second offensive on Vilnius On September 1, the German 8th and 12th Armies (335,696 men) launched an offensive on Grodno and Slonim. Parts of the 8th Army managed to overcome the swampy floodplain of the Bobr River in a day and approach the forts of Grodno. The German 12th Army crossed the Svislach River. The Germans were opposed by the 1st Army of Cavalry General Alexander Litvinov (270,504 men) in Grodno and the 2nd Army of Infantry General V. Smirnov (247,176 men) in the Lida directions. Already in the afternoon of September 1, the Grodno garrison began to fire from heavy guns; the paucity of heavy artillery of the German 8th Army made it necessary to concentrate fire only on forts I, III and IV; attacks on the forts of the 1st and 11th Landwehr Divisions were repulsed by the garrison. The next day, the Germans managed to capture the intermediate trenches between the forts and cross the Neman River, from the north, parts of the III Reserve Corps of the German 10th Army, advancing from Druskininkai, cut all roads to Vilnius, and the garrison began to leave the forts under the threat of encirclement. On September 3, German troops broke into the fortress, parts of the 20th Army Corps and the garrison retreated. Germans captured 3,600 prisoners and 6 heavy guns.
A new transition to the offensive of the armies of the Central Powers, the abandonment of Grodno, the German's exit to the Western Dvina and Lutsk forced Emperor Nicholas II to decide to assume the supreme command. This was announced on September 5. Infantry General Alekseyev was appointed the new Chief of Staff of the Supreme Commander, and Lieutenant General was appointed Quartermaster General of the Headquarters.
Hindenburg struck the main blow in the direction of Dvinsk, Vilnius, for which a redeployment of the Army of the Niemen and 10th Army was carried out with the concentration of almost the entire cavalry at the junction of these armies. In the ranks they numbered 502,357 men. In the Riga direction, the Russian 12th Army of the Northern Front (commander Infantry General V. Gorbatovsky, 185,989 men) defended, in the Dvina direction - the Russian 5th Army (commander general of cavalry Paul von Plehwe, 135,638 men). In the most difficult Vilnius-Minsk direction were the positions of the 10th Army of General of Infantry E. Radkevich (300,147 men).
German Švenčionys breakthrough Russian troops outnumbered the Germans in manpower; in addition, as at Gorlice–Tarnów offensive, the German struck at the most powerful Russian army. At the same time, the strike zone of the German 10th Army was chosen in such a way that in front of the strike group there was mainly Russian cavalry. The section of the front from Ukmergė to Wuqiang became such a place, the German I and XXI Corps were transferred here. On September 9, Russian positions were broken through at Širvintos to a depth of 20 km. The cavalry detachment of Lieutenant General N. Kaznakov was withdrawn by order of Plehve, the commander of the 5th Army, exposing the flank of the 10th Army, and on September 10 was driven back in battle with the German cavalry and Beckman's division and retreated behind Utena. The cavalry detachment of Lieutenant General was thrown back 10 km from the Širvinta River.
A 60-km gap formed between the flanks of the Russian 5th and 10th Armies, into which the German divisions rushed. On September 12, the German cavalry occupied Švenčionėliai (Novo-Sventiany), and the infantry of the I and XXI Corps went to Maišiagala and Pabradė. The 3rd Siberian Army Corps and the 2nd Finnish Rifle Division were transferred to the right flank of the 10th Army to help. On the left flank of the 10th Army, the 2nd and 26th Army Corps were withdrawn to Leipalingis.
As early as September 11, Alekseyev issued a directive on the transfer to the Švenčionys Offensive of the 2nd Army, which included corps withdrawn to the reserve from the 1st, 4th and 3rd Armies (14th, 27th, 29th, 36th and 4th Siberian Army Corps). But the concentration of troops was slowed down both by the condition of the roads as a result of the rains that had begun, and by the actions of the Germans on communications. The C-in-C of the Western Front armies, General of Infantry Aleksei Evert, ordered the 10th Army to concentrate a strong grouping on the right flank and go on the offensive north-west of Vilnius, and cover the gap with the armies of the Northern Front with the cavalry corps of the general from cavalry .
The right flank of the Army of the Niemen broke through to the Utena, creating a threat to Dvinsk. By September 14, the German 1st and XXXIX Reserve Corps pushed back the left wing of the Russian 5th Army to Dvinsk and captured a bridgehead along a 60-km arc from Lake Salava to Ilūkste: the strike group of the German 10th Army advanced to Vileyka and Molodechno, letting in the breakthrough, the cavalry corps of Manfred von Richthofen and O. von Garnier; Švenčionys and Narach were captured, but on the outskirts of Vilnius the Germans was repulsed by the forces of the Guards, 3rd Siberian and 5th Caucasian Corps.
Only on September 15, Oranovsky's cavalry corps appeared on the path of the German cavalry near the Sola and Smarhon, but the next day the Russian troops had to leave Vilnius under the threat of encirclement. By September 15, the German 12th, 8th and 9th Armies crossed the Neman River and occupied the entire western bank of the Shchara River. Army Group Mackensen (11th and Bug Armies, total 263,812 men) broke through the positions of the Russian 3rd Army.
On September 16, the German group of Johannes von Eben threw back Oranovsky's cavalry, but the onslaught of the Germans was stopped by the arriving units of the 2nd Army Corps. On the Ashmyanka River, the German cavalry division was stopped by the approaching regiments of the 5th Army Corps. The remaining divisions of the cavalry corps of Garnier and Richthofen occupied , Baruny, Vileyka and Smarhon with a front to the west and southeast, dedicating a squadron to undermine the Minsk-Smolensk railway (this was only possible on September 20).
On September 17, the German 3rd Cavalry Division reached the approaches to Molodechno, but 3-4 km from the city was stopped by the arriving units of the Russian 27th Army Corps. The German 1st and 4th Cavalry Divisions were met by the regiments of the 36th Army Corps that arrived in Ashmyany.
On September 17, the Supreme Commander Nicholas II (and in fact Alekseyev) issued a directive on the withdrawal from the night of September 18 over the next three nights of the Western Front's armies to the line of , Ashmyany, Novogrudok, Baranovichi, Vyhanaščanskaje Lake, and the 2nd Army was given an order to capture Švenčionys and Mikhalishki, reestablish contact with the 5th Army of the Northern Front and push back the Germans from Vileyka and Smarhon to Lida and Vilnius. To counteract the enemy cavalry and reach the rear of his grouping on the right flank of the 2nd Army, under the command of Oranovsky, the detachments of Kaznakov, princes K. Toumanov and S. Belosselsky-Belozersky (up to 8 divisions) joined. Under their cover, the 1st Army, also deployed to the north, was gathering in the Polotsk direction.
The maneuver of the Russian troops was facilitated by the mass withdrawal of German troops to the reserve to be sent to France - to repel the French offensive in Champagne and Artois - and against Serbia. The German High Command considered the operation against the Russian army completed, and by the end of September, 23 divisions left Russia, including 11 from the army group of August von Mackensen and 12 from the army group of Hindenburg. The remaining troops from September 20 ceased offensive operations and were withdrawn to the newly created fortified lines. On September 19-20, the Russian 2nd Army and the group of Infantry General Vasily Flug (Guards, 3rd Siberian, 2nd and 5th Army Corps) went on the offensive in order to drive the Germans out of the Ashmyanka and Neris rivers. The 27th, 36th and 4th Siberian Army Corps ousted Garnier's cavalry from Smarhon, but the offensive of Flug's corps was repulsed, the Eben group struck at the 3rd Siberian and 2nd Army Corps. Behind the second echelon cavalry were the German I and XXI Corps.
The Russian 10th Army retreated to Molodechno. On September 23, the Russian Headquarters issued a directive to attack the rear of the Germans from the town of Narach with the forces of the cavalry of the Russian 2nd Army; the Russian 5th Army was entrusted with covering the paths to Polotsk. From the German side, X. von Eichhorn ordered the pursuit of Radkevich's retreating army.