At the same time 25th Mechanized Corps, under the command of Major-General Semyon Krivoshein, was assigned to 21st Army from the Kharkov Military District.

[2] On 6 July a battle-group from the 21st Army (led by the 117th Rifle Division) crossed the Dnepr at Zhlobin south of Rahachow and attacked in direction of Babruysk.

Its 63rd Rifle Corps crossed Dnepr on pontoon bridges and recaptured Rahachow and Zhlobin, the first large towns to be retaken from German forces since the start of the invasion.

Zhlobin fell to Second Army on 14 August and the bridges over the Dnepr to the east of the town, though damaged, were taken in usable condition.

Rahachow was taken by Second Army the next day and a sizable Soviet force, predominantly from 63 Rifle Corps, became trapped in the resultant pocket.

Kuznetsov can't be blamed for that decision because his army was at that point already beaten by German forces and in full retreat.

[6] On 26 September Colonel-General Yakov Cherevichenko was appointed to the command of the residual forces of 21st Army that had escaped encirclement at Kiev.

By then it had become clear to Soviet high command that the main thrust of the German autumn offensive would not be directed at the Kharkov – Belgorod axis, the defence of which was assigned to South Western Front.

This German counterattack brought South Western Front's offensive north of Kharkov to an end and placed 21st Army on the defensive along the upper Donets for the rest of the winter and spring.

By late June 1942, 21st Army, with nine rifle divisions and a tank corps, occupied the northern flank of Southwestern Front along 100 kilometres of frontline east of Belgorod.

At the same time German mechanised forces that had broken through the centre of 40th Army began to move towards Stary Oskol.

Making effective use of rearguards, Gordov and his staff managed to slow the German advance sufficiently to enable the bulk of 21st Army to reach the Don in the Liski area, and to withdraw to the relative safety of the left bank of the river.

By the fourth week of July Sixth Army had secured bridgeheads on the left bank of the Don at its eastern extremity, and were preparing for an advance across the narrow strip of land to the Volga north of Stalingrad.

By this time the combat effectiveness of Sixth Army had been eroded by shortages of food, fuel and ammunition, yet the attacks against most of the perimeter made little progress.

Over the subsequent weeks the defensive positions of 21st Army south of Oboyan were to become the southern face of the Kursk salient.

At that time the army, under the command of Lieutenant-General Nikolai Krylov (chief of staff – Major-General Pavel Tikhomirov), included eight rifle divisions.

In order to destroy the Finnish Army and force Finland out of the war, the Stavka decided to conduct the two-pronged Vyborg–Petrozavodsk Offensive.

His task was to take command of forces facing the Finnish army's IV Corps in the western half of the frontline in the Karelian Isthmus north of Leningrad.

The offensive was planned to begin in early June, by which time 21st Army included nine rifle divisions subordinated to three rifle corps headquarters: On 9 June, 21st Army, supported by the guns of the Soviet Baltic Fleet, opened a massive artillery barrage against IV Corps' positions.

The next day, on 10 June, after a further artillery barrage, the Soviet 21st Army, spearheaded by 30th Guards Corps and with ample air and armoured support, opened the offensive on the Valkeasaari sector, which was defended by the 1st Infantry Regiment of the Finnish 10th Division.

During the day, the Soviet units captured frontline trenches and destroyed fortifications, shattering the first Finnish "Main line" of the breakthrough sector.

IV Corps was forced back to its second defence line and the Finns were obliged to send in reinforcements to try to stabilise their defensive position.

The renewed Soviet offensive began on 25 June against IV Corps' defences in the Tali area, culminating into the Battle of Tali–Ihantala.

After four days of intense fighting, during which both sides fed reserves into the battle, the Finns were pushed back, but their lines did not break under the heavy Soviet manpower.

By 6 July, after four weeks of intense fighting and after having sustained heavy casualties, 21st Army's offensive capacity was exhausted as a result of their swift advance.

The Front's main offensive efforts during that time had been directed towards expanding a bridgehead over the Vistula in the Sandomierz area, and in attempting to advance its left wing through the northern Carpathians into Slovakia.

Thereafter the priority for 1st Ukrainian Front was to cross the Oder and to advance to the river Neisse, from where it was planned it would launch its final offensive towards Dresden and central Germany.

As the axis of 1st Ukrainian Front's offensive shifted to the west, 21st Army found itself on a relatively inactive sector of the frontline.

In April, this frontline stabilised again as 1st Ukrainian Front's resources were directed to the west for the impending offensive across the Neisse into central Germany.

Over the subsequent four days, 21st Army advanced 70 kilometres, taking Wałbrzych and crossing the Czech border to reach Jaromerz by the war's end on 9 May.