The 126th Rifle Division was first formed as an infantry division of the Red Army on August 14, 1939, in the Moscow Military District, based on the shtat (table of organization and equipment) of the following month. In June 1940 it made up part of the force that occupied Latvia. It remained in the occupied Baltic states, being assigned to 11th Army in Lithuania in early 1941. At the start of the German invasion it was in the vicinity of Kaunas and was struck on the opening day, suffering heavy losses, then forced to retreat to the east, soon being reassigned to Northwestern Front's 27th Army. Shortly after it was moved to 22nd Army of Western Front, and fought under those commands near Velikiye Luki and Toropets, escaping from encirclement in the process. After retreating past Andreapol the front stabilized and during September the 126th was substantially rebuilt, but lost much of its strength when it was again encircled in the early part of Operation Typhoon. After escaping it was reassigned to 16th Army, but in November it was decided to use its remaining assets to reinforce other units of the Army and on December 13 it was disbanded.

A new division named after Marshal K. E. Voroshilov began forming on September 1, 1941, in the Far Eastern Military District and in January 1942 it was redesignated as the new 126th. It remained in the Far East until May when it was moved west, eventually arriving south of Stalingrad as the German drive on the city was well underway. In early August it was assigned to 64th Army in Southeastern Front, battling against the 4th Panzer Army and gradually being pushed to the outskirts of the city while taking very heavy casualties. During September and October it fought positional battles in the Beketovka bridgehead south of the city while rebuilding its strength, now as part of Stalingrad Front, but in preparation for Operation Uranus it was shifted well to the south, joining 51st Army, which was facing the forces that were about to become Romanian 4th Army. The division successfully smashed through the Romanian positions on the first day of the offensive then advanced to the southwest, helping to form the outer encirclement front but soon coming under attack from 4th Panzer as it attempted to relieve the Stalingrad pocket. After the failure of Operation Winter Storm the division with its Army began a counteroffensive toward Rostov-on-Don as part of Southern Front. Once that city was liberated in mid-February 1943 the division advanced to the Mius River, where it encountered the defenses erected by Army Group South after first losing Rostov in December 1941. It was halted along this line and spent several months in a much-needed replenishment, during which it was reassigned to 5th Shock Army. Under this command it took part in both the abortive July offensive and the successful August offensive into the Donbas, and was awarded a battle honor. Returning to 51st Army it played a key role in the capture of Melitopol and was awarded its first Order of the Red Banner. Following this it advanced with the rest of the now-4th Ukrainian Front to the approaches to the Crimea, but stalled there during the winter of 1943/44, being reassigned to 2nd Guards Army in February. In April it took part in the offensive that pushed through the Isthmus of Perekop, winning the Order of Suvorov in the process, and then in the recapture of Sevastopol, for which it was awarded a second Order of the Red Banner. With the conclusion of this campaign it left 4th Ukrainian with its Army and was sent well to the north, joining 1st Baltic Front in July during its advance into the Baltic states. Two of its regiments distinguished themselves in the fighting around Šiauliai but also suffered heavy losses. In November it was transferred to 43rd Army, which itself was moved to 3rd Belorussian Front after the start of the invasion of East Prussia. In February 1945 it was briefly reassigned to 39th Army, but soon returned to the 43rd for the duration of the war. During early April it played a leading role in the storming of Königsberg, for which several of its subunits would receive decorations. With 43rd Army the 126th was reassigned to 2nd Belorussian Front in the last days of the war, and this became the Northern Group of Forces postwar. In December the division returned to the Crimea, where it was converted to a mechanized division in 1946. However, during further reorganizations over the following decades the "126th" number reappeared until the division was finally disbanded in 1996.

1st Formation The division was formed at Moscow in the Moscow Military District on August 14, 1939, based on a cadre from the elite 1st Moscow Rifle Division's 2nd Rifle Regiment.Charles C. Sharp, "Red Legions", Soviet Rifle Divisions Formed Before June 1941, Soviet Order of Battle World War II, Vol. VIII, Nafziger, 1996, p. 64 Komdiv Nikolai Aleksandrovich Sokolov, who had been serving as deputy commander of the 68th Mountain Rifle Division, was given command within days but was moved to the 11th Rifle Division on February 4, 1940. The division saw several more changes of command until January 27, 1941, when Maj. Gen. Mikhail Andreevich Kuznetsov took over. In mid-June, 1940, it was part of the force that occupied Latvia. At the time of the German invasion on June 22, 1941, the division was under direct command of 11th Army.Combat Composition of the Soviet Army, 1941, p. 7 Its order of battle was as follows: 366th Rifle Regiment 539th Rifle Regiment (later 690th) 550th Rifle Regiment 358th Light Artillery Regiment (until October 30, 1941) 501st Howitzer Artillery Regiment (until October 25, 1941)Sharp, "Red Legions", p. 64 426th Howitzer Artillery Regiment (from October 10, 1941) 265th Antitank Battalion 286th Antiaircraft Battalion (later 240th) 198th Reconnaissance Battalion 175th Sapper Battalion 233rd Signal Battalion 222nd Medical/Sanitation Battalion (later 212th) 130th Chemical Defense (Anti-gas) Company 101st Motor Transport Company (later 230th Battalion) 195th Field Bakery 873rd Field Postal Station 139th Field Office of the State Bank At this time it was near the left flank of the Baltic Special Military District with its main forces in the Žiežmariai area, tying in to the 128th Rifle Division on its left flank and the 188th Rifle Division on its right.Artyom Drabkin & Alexei Isaev, Barbarossa Through Soviet Eyes, trans. C. Summerville, Pen & Sword Books, Ltd., Barnsley, UK, 2012, p. xi

The District commander, Col. Gen. F. I. Kuznetsov, had disregarded the instructions of the NKO and General Staff to avoid any action that might be taken as a provocation. On June 15, alarmed by intelligence reports of the German buildup, issued orders to increase force readiness along the frontier. Without directly mentioning the buildup he stated, "Today, as never before, we must be fully combat ready. Many commanders do not understand this. But all must firmly and clearly understand that at any moment we must be ready to fulfill any combat mission." After receiving further intelligence two days later Kuznetsov ordered his forces to full military readiness on June 18. While his actions were brave in going against orders from the top and militarily correct, it's unlikely that they made any real difference when the war began.David M. Glantz, Stumbling Colossus, University Press of Kansas, Lawrence, KS, 1998, pp. 104-05

At the outset of the invasion the division had a mixed regiment, consisting of 3rd Battalion, 550th Regiment, 2nd Battalion, 366th Regiment, and 3rd Battalion, 539th Regiment, plus part of the divisional artillery deployed forward to the frontier. The remainder was preparing for a march to woods near Prienai for field exercises. Before this could begin the mixed regiment was struck by the VI Army Corps and largely destroyed, while the XXXIX Motorized Corps forced a gap between the 126th and 128th. Jr. Sgt. Sergei Matsapoura, a gun layer in the 358th Artillery, recalled:By the evening, 11th Army had been largely encircled or scattered. While most remaining formations retreated to the north the 126th was forced off to the east of Kaunas, and by July 10 it had been reassigned to 27th Army along the Daugava River, near Dzisna, with less than 2,000 men remaining under command. Within this Army it was subordinated to the 29th Rifle Corps.Combat Composition of the Soviet Army, 1941, p. 23

Battles for Nevel and Velikiye Luki Vitebsk fell on July 11, and 29th Corps was soon transferred to Lt. Gen. F. A. Ershakov's 22nd Army of Western Front which was attempting to hold what remained of the Daugava line from the Polotsk Fortified Region east toward Haradok. The 126th was reported as fighting along a line from Ignatovko to Kulikovo. The Front commander, Marshal S. K. Timoshenko, issued orders late on July 12 for Ershakov to carry out a counterattack the following morning with two divisions and supporting artillery from the Haradok area south toward Vitebsk. This plan was stillborn when the LVII Motorized Corps, backed by the L and XXIII Army Corps drove the Army from its defenses along the Dvina northwest of Polotsk, cut it into two parts, enveloped its flanks and threatened both parts with encirclement. With only six divisions to defend a front 274 km wide Ershakov was soon in full retreat as the panzers drove northward toward Nevel.Glantz, Barbarossa Derailed, Vol. 1, Helion & Co., Ltd., Solihull, UK, 2010, Kindle ed., chs. 2, 3

Nevel was taken by LVII Motorized on the morning of July 16 which left 29th Corps and eight other divisions cut off and isolated between that town and Vitebsk. As the German commanders debated the size of the encircled forces and exactly how best to deal with them while also carrying out their other objectives, the divisions did their best to escape in the general direction of Velikiye Luki, aided by the difficult terrain in the region. On July 19 the 19th Panzer Division captured the city but overnight elements of 22nd Army attacked and overran the thin screen being held around Nevel by 14th Motorized Division, allowing the Army's encircled 62nd Rifle Corps to escape to the east. This pressure also forced 19th Panzer to abandon the city on July 21 and Ershakov triumphantly signalled the commander of 62nd Corps:This overlooked victory was the first large city liberated by the Red Army. Ershakov now attempted to create a new defense line along the Lovat River although his 51st Rifle Corps had been reduced to remnants.Glantz, Barbarossa Derailed, Vol. 1, Kindle ed., chs. 3, 6

In the course of this fighting General Kuznetsov was organizing a counterattack near Velikiye Luki when he was severely wounded; he died of his wounds on August 6. At the time the division was entirely without organic artillery and was forced to attack without any preparation, suffering heavy casualties with no success.Aleksander A. Maslov, Fallen Soviet Generals, ed. & trans. D. M. Glantz, Frank Cass Publishers, London, UK, 1998, pp. 18, 249 He was replaced on July 22 by Col. Efim Vasilevich Bedin, who had been in command of the 550th and then the 690th Rifle Regiments.