'Koltso' was the Soviet undertaking by General Polkovnik Konstantin K. Rokossovsky’s Don Front to destroy Generaloberst (from 31 January Generalfeldmarschall) Friedrich Paulus’s 6^th Army and part of Generaloberst Hermann Hoth’s 4^th Panzerarmee trapped in the Stalingrad pocket since the success of the Soviet 'Uran' cut-off operation and the failure of the German 'Wintergewitter' (i) relief operation (10 January/2 February 1943).

On 4 December, in Moscow, Iosif Stalin and General Polkovnik (from 18 January 1943 General) Aleksandr M. Vasilevsky, the chief of the general staff, agreed that the time was now ripe for the destruction of the isolated 6^th Army, and Stalin gave the operation which was planned the codename 'Koltso'. The Soviet plan was to split the pocket of trapped Germans with a drive through their centre from west to east, and then to destroy the northern and southern half-pockets thus created in sequential offensives along the lines of a plan submitted by General (from 18 January 1943 Marshal Sovetskogo Soyuza) Georgi K. Zhukov, the deputy chairman of the high command, deputy commander-in-chief of the Soviet armed forces and first deputy people’s commissar of defence, on 29 November. The main effort was to be a thrust from the west by Rokossovsky’s Don Front, which was to be strengthened with General Leytenant Rodion Ya. Malinovsky’s 2^nd Guards Army, currently the most powerful Soviet field army, from the Stavka reserve and be ready to attack on 18 December.

'Saturn' had not started and 'Koltso' was not ready when the Armeegruppe 'Hoth' of Generalfeldmarschall Erich von Manstein’s Heeresgruppe 'Don' began its 'Wintergewitter' (i) attempt to break though for the relief of the German forces trapped at Stalingrad. By Rokossovsky’s account, Vasilevsky was at the headquarters of the Don Front on the morning of 12 December as 'Wintergewitter' (i) began and, immediately after news of the German offensive arrived, telephoned Stalin to have the 2^nd Guards Army transferred to Stalingrad Front. Vasilevsky says he did not make the request until later in the day and did not get the Stavka’s decision until that night. The launch of 'Wintergewitter' (i) paved the way for the recasting of 'Saturn' as the more ambitious 'Malen’kii Saturn', and the loss of the 2^nd Guards Army put 'Koltso' into abeyance, at least in the form in which it had originally been conceived.

During the planning for 'Don' and the enlarged 'Malen’kii Saturn' in the last days of December 1942, the Stavka revived 'Koltso' against the German pocket at Stalingrad pocket. After General Polkovnil Andrei I. Eremenko’s Stalingrad Front relinquished three of its armies for 'Don' on 1 January, Rokossovsky’s Don Front controlled the entire perimeter of the pocket with seven armies with 281,000 men. General Polkovnik Nikolai N. Voronov took over as Stavka representative with Don Front. As Rokossovsky would now not have the services of a fresh mobile formation, such as the 2^nd Guards Army had been, 'Koltso' had to be revised. The initial objective was still to split the pocket on a west/east line, but this would now be achieved by stages instead of in a single sweep and would be directed more against the weaker western and southern faces of the pocket. In the first stage, General Leytenant Pavel I. Batov’s 65^th Army would deliver the primary thrust with a drive from the north-west to the south-east toward Karpovskaya Station. In the second stage, General Major Ivan M. Chistyakov’s 21^st Army would take over and lead a drive to Voroponovo Station, and in the third five armies would storm in from the north-west, west, and south-west with the object of splitting what was left of the pocket by making contact in Stalingrad with General Leytenant Vasili I. Chuikov’s 62^nd Army. Originally scheduled to begin on 6 January and to take seven days, 'Koltso' was then postponed to 10 January, and on 8 January Rokossovsky sent Paulus a surrender ultimatum, which was rejected.

By 1 January 1943 the 6^th Army was in the throes of a lingering death from cold, starvation and exhaustion. Between 1 and 23 December, the airlift of supplies to the 6^th Army had averaged a mere 90 tons per day and on only one day, 7 December, did they reach the army’s daily minimum requirement of 300 tons. In the first three weeks of January, the average was 120 tons per day, a figure wholly inadequate to maintain the 6^th Army.

Even so, the 6^th Army was as yet not entirely at the mercy of the Soviet forces surrounding it. All of the Don Front’s armies had been in constant action for some time, and losses had combined with the weather, hunger and fatigue to take their toll of them. In fact the 6^th Army even had some advantages. One was that the pocket encompassed nearly all of the built-up areas in and around Stalingrad, and the German troops therefore had a modicum of shelter and could obtain wood for fuel from demolished buildings, while the Soviets had none. The Germans also had the advantage of field fortifications they had built during the siege and, particularly, of the Soviet defence lines built during the summer. Between the lines, the terrain was generally flat and treeless, but was cut by deep gullies, which favoured the defence.

For 'Koltso', therefore, Chistyakov’s 21^st Army, General Leytenant Ivan V. Galanin’s 24^th Army, Batov’s 65^th Army and General Leytenant Aleksei S. Zhadov’s 66^th Army of the Don Front were reinforced by General Leytenant Nikolai A. Gagen’s 57^th Army, Chuikov’s 62^nd Army and General Leytenant Mikhail S. Shumilov’s 64^th Army of Eremenko’s Stalingrad Front, which had been redesignated as the South Front on 1 January 1943.

The Soviet planning was undertaken at a high level by the Stavka in Moscow when the Soviet leadership came to appreciate that its first impression, namely that only a few German divisions had been trapped in Stalingrad, was erroneous and that the encirclement in fact comprised the whole of the 6^th Army and a large part of the 4^th Panzerarmee. The Soviet planning called for the 'Wintergewitter' (i) relief attempt (controlled by von Manstein’s Heeresgruppe 'Don' and spearheaded by the two Panzer divisions of General Friedrich Kirchner’s LVII Panzerkorps of the Armeegruppe 'Hoth' of the 4^th Panzerarmee) to be defeated comprehensively before the beginning of 'Koltso', and for Malinovsky’s 2^nd Guards Army to transfer formations to the Don Front.

As indicated above, during this time a very considerable air transport operation was mounted by the Luftwaffe, under the personal control of Reichsmarschall Hermann Göring, to fly into the beleaguered forces all necessary fuel, food, ammunition and other supplies, on their return trips the aircraft flying out some 25,000 wounded. The 6^th Army occupied a pocket measuring some 40 miles (64 km) in east/west length, and about 20 miles (32 km) in north/south depth, and this area contained two major airfields (Gumrak and Pitomnik, the latter having the pocket’s only night-flying capability) and five smaller airstrips. At first the aircraft had only some 150 miles (240 km) to fly, but as Soviet successes against the 4^th Panzerarmee and 6^th Army steadily increased the gap between the trapped German formations and the rest of Germany’s capability on the Eastern Front, this distance increased eventually to 300 miles (485 km), the need to carry additional fuel reducing the aircraft’s freight loads and increasing the chance of interception by the increasingly potent fighter force of General Polkovnik Sergei I. Rudenko’s 16^th Air Army. Thus the average daily delivery of supplies had fallen from 140 tons in mid-December to 60 tons in mid-January, when Göring was replaced in supervisory command of the operation by Generalfeldmarschall Erhard Milch, who managed to boost deliveries to about 80 tons per day before the Soviet ring closing in around the city cost the Germans the airfields and made necessary a recourse to paradrops.

During the whole of its airlift effort the Luftwaffe lost some 490 essentially irreplaceable transport and bomber-transport aircraft, together with most of their experienced and therefore invaluable crews.

Under cover of a rolling artillery barrage in whose wake followed large quantities of armour and infantry, at 09.00 on the morning of 10 January, Rokossovsky was at the headquarters of Batov, commander of 65^th Army, when 65^th, 21^st and 24^th Armies began 'Koltso' against the western extremity of the German pocket, which was held in the north by elements of General Walter Heitz’s VIII Corps and in the south by elements of General Hans-Valentin Hube’s XIV Panzerkorps. The Soviet assault had the benefit of operating under an umbrella of almost total air superiority and, despite a number of German counterattacks, the first day of the operation brought the Soviets territorial gains in the order of 2 to 3 miles (3.2 to 4.8 km). This was disappointing for Rokossovsky, who had demanded a greater advance, but also very dismaying for Paulus who, during the night which followed, reported that after the day’s fighting there was clearly no longer any prospect that the 6^th Army could hold out until the middle of February, and therefore that relief would have to come much sooner than had been planned; that the promised quantity of supplies would have to be delivered; and that fresh battalions would have to be flown in at once to replace those lost in the bitter fighting.

The bitterness of the fighting was mirrored by the acute nature of the winter weather, in which strong winds and snow storms were frequent in temperatures that seldom rose above -22° F (-30° C). The conditions also hampered the Germans considerably more than the Soviets, for the former could not dig defensive positions and the latter relished the frozen ground for the good going it provided for their armour. The heavy losses suffered by Generalleutnant Heinrich Deboi’s 44^th Division, Generalleutnant Carl Rodenburg’s 76^th Division and Generalmajor Hans Georg von Leyser’s 29^th Division (mot.) on the first day of the attack were reported to the Oberkommando des Heeres, but this body’s only response from far-off Berlin an instruction about the line from which the 6^th Army was not to fall back without receiving specific permission.

On or about 10 January, Paulus ordered the 6^th Army's Soviet prisoners of war, for whom there was no food, to be returned to the Soviet forces, but this did not happen because the men were either too frightened to return to their compatriots, by whom they would be treated as traitors, or were turned back by the besieging formations.

The Germans managed to prevent an outright breakthrough in the next two days by falling back under pressure some 19 miles (30.5 km) to the line of the Rossoshka river northward from its junction near Karpovka with the Karpovka river to create the Chervlennaya river. When they reached the line of the Rossoshka river on the night of 12 January, the Soviet armies, which had maintained the momentum of their offensive by night and day, had completed the first stage of 'Koltso', but now faced, on the river, what had been the original outer ring of the Soviet defences of Stalingrad. On 13 and 14 January, Rokossovsky regrouped to shift his primary effort to the 21^st Army, which was now to strike due east toward Voroponovo Station while the 65^th Army aimed to advance past Pitomnik.

It was after the 65^th and 21^st Armies, joined on the north by the 24^th Army and on the south by the 57^th and 64^th Armies, had broken the Rossoshka river line on 15 January, and after repeated pleas from Paulus, that Hitler appointed Milch to supervise the air supply effort for the 6^th Army. In the appointment, Hitler gave Milch authority to issue orders to all branches of the German military and, for the first time, established a command powerful enough to override all other claims on aircraft, fuel and ground crews and thus to organise the air supply on the scale which had been promised for Stalingrad. By this time daylight landings in the pocket had become very dangerous, and in another four days, the forces of the South-West Front took the main air supply base at Tatsinskaya, forcing the German transport aircraft to operate from airfields at Rostov-na-Donu and Novocherkassk, more than 200 miles (320 km) from the pocket.

Early on 16 January the 6^th Army lost Pitomnik airfield, the better of its two airfields within the pocket. Six of the 14 German fighters based there took off under fire. Five attempted to land and crashed on the airstrip at Gumrak, which was still in the hands of the 6^th Army; the pilot of the sixth fighter flew to the west, thus ending the fighter defence over the pocket. On 17 January, Luftflotte IV temporarily suspended landings at Gumrak after a pilot mistakenly reported that the German forces were retreating past it.

Gumrak was also frequently out of service as a result of snow and the cratering of its operational surface by Soviet bombing. From this point onward, the German air supply effort was therefore limited largely to loads either parachuted or free-dropped from aircraft. This method was logistically complex at the loading end of the operation, demanded specialised equipment as well as specially trained packers and despatchers, and rendered the aircraft especially vulnerable to anti-aircraft fire as well as fighter attack as they made their dropping run in straight and level flight at low altitude. Even when all went well, the system was by its very nature uneconomical as well as inaccurate, much of the dropped supplies being lost or even landing among the attacking Soviet formations. The 6^th Army was so disorganised and lacking in fuel by this stage of the siege, and its men so weak because of the cold and for lack of food, that even the loads which landed accurately were often not collected and redistributed.

By 13 January the Soviet forces west of Stalingrad had reached a basically north/south line extending between Borodkin in the north and a point north-west of Betekovka, a 'suburb' of Stalingrad, in the south. It has been reported that on 17 January the Don Front sent a second surrender demand to Paulus, but this offered terms which the Soviets could not have kept and was therefore not believed in Stalingrad.

The Don Front completed the second stage of 'Koltso' on 17 January as it reached the line extending from Voroponovo Station to the north-west as far as Rossoshka. This meant that the area of the German pocket had been reduced by about two-thirds, but the Soviet forces had used all of the seven days which had been allotted for the completion of 'Koltso'. Even so, the 6^th Army had managed once more to hold its front together and was now, in the south, occupying the original main defence line for Stalingrad. Something had gone wrong with the Soviet planning, and Rokossovsky placed the blame on erroneous intelligence. The Don Front had gone into the offensive. so Rokossovsky claimed, in the belief that the 6^th Army possessed only 80,000 to 85,000 men, but events had now revealed that it possessed something closer to 200,000 men.

For four days after 17 January, Rokossovsky regrouped his forces. During the pause, Paulus reported on 20 January, that the 'fortress' of Stalingrad could hold out for no more than a few days longer, that in some sectors the defenders had all been destroyed, and that the Soviets could march through the front wherever and whenever they wished.

The final stage of 'Koltso' started on 22 January. the 5^th Army’s infantry, driving forward from the south-west on a 3-mile (4.8-km) front along the west/east railway, broke through at Voroponovo Station and marched eastward into Stalingrad with its battle flags flying. To close the gap this time was impossible for the Germans of General Max Pfeffer’s IV Corps, who had exhausted their last supplies of ammunition, and who could be neither reinforced nor resupplied from other sectors.

During the night of 22/23 January Paulus radioed to Hitler via General Kurt Zeitzler, the chief-of-staff of the Oberkommando des Heeres, that the 6^th Army's rations were exhausted and more than 12,000 wounded lay unattended in the pocket. Paulus also asked what orders he should give to troops who had no ammunition and were subjected to large-scale attacks supported by heavy artillery fire. Paulus added that he needed an answer as a matter of the greatest urgency as the disintegration of his command had already started in some places. Paulus ended with the statement that there remained confidence in the leadership.

Hitler answered that surrender was out of the question, that the troops had to defend themselves to the last, and that the size of the 'fortress' was to be reduced, if this was possible, so that it could be held by the troops still capable of fighting. Hitler added that the courage and endurance of the 'fortress' had made it possible to establish a new front and begin the preparation of a counter-operation, and that the 6^th Army had thus made an historic contribution to Germany’s greatest struggle.

Thus Paulus’s veiled request for permission to surrender was ignored by the German leader who, as late as 24 January, refused to consider the possibility of the 6^th Army breaking out to the west in small groups in an effort to reach Heeresgruppe 'Don' or, failing that, to operate as guerrilla forces in the Soviet forces' rear areas.

Meanwhile on the line of the upper Don river there had erupted a new Soviet counter-offensive even more dangerous than those of a slightly earlier time. This 'Skachok' had started on 13 January, and was in effect destroying Generalfeldmarschall Maximilian Reichsfreiherr von Weichs’s Heeresgruppe 'B' and also threatening the survival of Heeresgruppe 'Don' and, still farther to the south, Generalfeldmarschall Ewald von Kleist’s Heeresgruppe 'A' in the Caucasus.

As the front line was pushed back from the west, the inner city of Stalingrad, which after months of bombardment had a hellish appearance, became a scene of ghastly horror. The 6^th Army reported 20,000 wounded wholly lacking care, and an equal number of starving, freezing and unarmed stragglers. Those who could took shelter in the basements of the ruins, where hundreds of tons of overhead rubble provided protection against the constant downpour of artillery shells. There, in darkness and cold, the sick, the mad, the dead and the dying were massed, those who could move daring not to do so for fear of losing their places. Over the tallest of the ruins in the centre of Stalingrad, the 6^th Army ran out the Reich battle flag 'in order to fight the last battle under this symbol'.

Meanwhile, in Stalingrad proper Chuikov’s 62^nd Army, half encircled in the west by the 6^th Army and still cut into two parts, was nonetheless pinning a number of German divisions. The Germans were prevented from moving to the north or to the south by the offensive operations of Zhadov’s 66^th Army and Shumilov''s 64^th Army, and Rokossovsky’s four other armies continued their offensives from the west.

On 26 January, when the remnants of the German defence rested on General Karl Strecker’s XI Corps in the north, General Walter von Seydlitz-Kurzbach’s LI Corps in the centre and Pfeffer’s IV Corps in the south, the 62^nd Army took Mamai Hill, and here linked with the armour of the 21^st Army, advancing from the west, to split the German pocket in two. Thereafter, the XI Corps formed a perimeter around the tractor works on the northern edge of the city while the headquarters of the 6^th Army and the IV Corps, VIII Corps and LI Corps dug themselves in around and to the north-west of the main railway station. The IV Corps, which had been holding the southern perimeter, was destroyed on that day by a Soviet push across the Tsaritsa river from the south. By this time the 6^th Army had requested that the air force drop only food: artillery ammunition was no longer needed as there were too few guns to make use of any such delivery. The 6^th Army stopped issuing rations to the wounded on 28 January to preserve the strength of the fighting troops.

On the same day the main theme of the midnight situation conference at Hitler’s headquarters was Hitler’s desire to have a 6^th Army reconstituted quickly, using as many survivors of the original army as could be found.

By 29 January, the southern pocket was split, leaving Paulus, his staff and a small miscellany of troops in an enclave in the south, and the remnants of the LI Corps and VIII Corps in the north. The XIV Panzerkorps ceased to exist during this day. In the night, 10 small groups of men departed in a forlorn attempt to make their way out to the west across almost 200 miles (320 km) of Soviet territory. By the next night, the LI Corps and VIII Corps had been further compressed into a small area around a former Soviet army engineer barracks, where they surrendered on the morning of the following day. The headquarters of the 6^th Army lay inside a 300-yard (275-m) perimeter around the Red Square held by the survivors of the 194^th Grenadierregiment. At 06.15 on the morning of 31 January, the radio operator at the headquarters of the 6^th Army, located in the basement of the Univermag department store on Red Square, transmitted that the Soviets were at the door, and that preparations were being made to destroy the radio equipment. Just one hour later, the last transmission from the 6^th Army stated that the equipment was being destroyed. Paulus surrendered himself, his staff and the troops with him, to the 38^th Motor Rifle Brigade as this reached department store in Red Square, but refused to order the XI Corps to do the same. Promoted to field marshal just the day before, he became the first German officer of that rank ever to have been taken prisoner. Hitler had expected the promotion to persuade Paulus to adopt a different course, and now declared that Paulus had done an about-face on the threshold of immortality.

In the pocket around the tractor works, the surviving 33,000 men of Strecker’s XI Corps continued to resist for another 48 hours. On 1 February, Hitler demanded that the corps fight to the last man with the exhortation that 'every day, ever hour that is won benefits the rest of the front decisively'. At 08.40 on the next morning, Heeresgruppe 'Don' received a final message from Strecker to the effect that the XI Corps' six divisions had done their duty to the last.

In the Stalingrad pocket the Germans lost somewhat more than 200,000 men, though the exact total has never been exactly established. During the fighting, 30,000 wounded men were flown out. The Soviet accounts state that 147,000 German dead were counted on the battlefield and 91,000 Germans were taken prisoner, the latter total including 24 generals and 2,500 other officers, almost all of them sick and/or wounded if not badly malnourished. Only a few of the 91,000 men probably taken prisoner ever returned to Germany after incarceration in the depths of the USSR. The Soviets never released figures of their own losses in the Stalingrad battle. However, if the casualties given for two units, the III Cavalry Corps and VIII Cavalry Corps (36% and 45% respectively) in the period between 19 November and 2 December are in any way representative, the Soviet losses must have been very substantial.

An impression of the magnitude of 'Koltso' can be derived from the Don Front’s ammunition expenditure between 10 January and 2 February 1943: 911,000 rounds of artillery shells in calibres up to 152 mm (5.98 in), 990,000 mortar bombs, and 24 million rounds of machine gun and rifle ammunition.

As Hitler himself frequently stated, the 6^th Army had performed a service at a critical time by tying down several hundred thousand Soviet troops. What cannot be denied, however, was that this was a service performed for the wrong reasons. Hitler did not keep the 6^th Army at Stalingrad for even so modestly valid a military purpose, but rather because he was concerned entirely with his belief in the need to preserve the appearance of success for a campaign which, he already knew, had failed. At the last, having kept what was happening at Stalingrad from the German public until after the start of 'Koltso', he had nothing better in mind than that he believed a fight to the last man would be less damaging to the national morale and his own image than a surrender. Certainly one can imagine a less disastrous development of the battle on the southern flank of the Eastern Front for Germany if the 6^th Army had been allowed to get its 20 divisions away from Stalingrad in time.

With the loss of its 6^th Army at Stalingrad, Germany had suffered a vast psychological as well as physical blow, and the strategic tide of the war on the Eastern Front had swung decisively to the Soviets.