'Saturn' (i) was a Soviet unrealised plan to recapture Rostov-na-Donu on the lower reaches of the Donets river at the same time as the elimination of the German pocket in Stalingrad and so cut off significant portions of Generalfeldmarschall Ewald von Kleist’s Heeresgruppe 'A' and Generalfeldmarschall Maximilian Reichsfreiherr von Weichs’s Heeresgruppe 'B' (23 November/December 1942).

After it has passed the operational responsibility of the Stalingrad sector to Generalfeldmarschall Erich von Manstein’s Heeresgruppe 'Don', Heeresgruppe 'B' retained one critical role, namely the protection of the rear of its neighbours to the south, Heeresgruppe 'Don' and Heeresgruppe 'A'. On the critical 200-mile (320-km) length of the Don river downstream from Voronezh to Veshenskaya, this responsibility fell to Altábornagy Gusztáv Jány’s Hungarian 2^nd Army and Generale d’Armata Italo Garibaldi’s Italian 8a Armata. How well these two allied formations might be expected to cope with a Soviet offensive was highly predictable because the Romanians were considered the best of the German allies, somewhat ahead of the Hungarians and Italians.

Heeresgruppe 'Don' and Heeresgruppe 'A' were both now in extremely vulnerable positions, for they were wholly reliant in logistical terms on the few railway lines which extended into the steppe regions to the east of the great Dniepr, Donets and Don rivers. The critical points on these rail lines were the river crossings: all traffic heading to the east out of the Dniepr river bend depended on the bridges at Dniepropetrovsk and Zaporozhye. The distances from Dniepropetrovsk to the Soviet line at Novaya Kalitva, in the centre of the sector held by the Italian 8a Armata, was 250 miles (400 km), to the front held by Heeresgruppe 'Don' on the Chir river 330 miles (530 km), and to the left flank of Heeresgruppe 'A' 580 miles (935 km). The Soviets had no needed to strike as far to the west as Dniepropetrovsk, however, for on the left flank of Heeresgruppe 'Don' their forces were within 80 miles (130 km) of three crossings of the Donets river, namely those at Voroshilovgrad, Kamensk-Shakhtinsky and Belokalitvenskaya, and a march of 150 miles (240 km) from the left flank of Heeresgruppe 'Don' would carry them to Rostov-na-Donu near the mouth of the Don river. Both Heeresgruppe 'A' and Generaloberst Eberhard Raus’s 4^th Panzerarmee were tied to the railway through Rostov-na-Donu, and the left flank of Heeresgruppe 'A' was 350 miles (565 km) and the right flank of the 4^th Panzerarmee 220 miles (355 km) from Rostov-na-Donu.

Inevitably, the strategic oddity of the German situation was of course perceived by the Soviets, and during the night of 23/24 November, Iosif Stalin instructed General Aleksandr M. Vasilevsky, the chief of the Soviet general staff, to develop a plan for an offensive by General Polkovnik Nikolai F. Vatutin’s South-West Front (General Leytenant Vasili I. Kuznetsov’s 1^st Guards Army, General Leytenant Pavel A. Rotmistrov’s 5^th Tank Army and General Leytenant Ivan M. Chistyakov’s 21^st Army) and the left wing of General Leytenant Filipp I. Golikov’s Voronezh Front from Nizhne Chirskaya toward Millerovo and Rostov-na-Donu. It seems that on the same night Stalin also spoke to General Major Kirill S. Moskalenko, commander of 1^st Guards Army, about a still more ambitious offensive to liberate Kharkov and the Don basin. In the last week of the month, Vasilevsky and General Polkovnik Nikolai N. Voronov, who would be co-ordinating the operation as Stavka representatives, worked on the plan with the two front commanders. General Soyuza Georgi K. Zhukov, the first deputy commissar for defence, who had gone to the Kalinin and West Fronts to supervise 'Mars', nevertheless remained in close touch with Stalin and Vasilevsky.

On 2 December, Stalin and the Stavka approved the plan as 'Saturn' as successor to 'Uran', and set the readiness date as 10 December for an undertaking designed to encircle the Italian 8a Armata and those formations of Heeresgruppe 'Don' inside the Don river bend and, by taking Rostov-na-Donu and the lower reaches of the Don river, to cut off the 4^th Panzerarmee and Heeresgruppe 'A' in the Caucasus. On the right, the South-West Front’s 1^st Guards Army and 3^rd Guards Army (the latter to be formed by dividing the 1^st Guards Army and adding infantry divisions and a mechanised corps from the reserves) was to break through the Italian 8a Armata's left flank near Boguchar, strike almost straight to the south to Millerovo, cross the Donets river at Kamensk-Shakhtinsky, and continue to the south in the direction of Rostov-na-Donu. On their right, the Voronezh Front’s 6^th Army would provide flank cover and advance on Voroshilovgrad. To form the second arm of the envelopment, the 5^th Tank Army was to cross the Chir river and advance along the right side of the Don river’s lower reaches to Rostov-na-Donu.

On 4 December, Stalin and Vasilevsky also decided that the time was ripe for the destruction of Generaloberst Friedrich Paulus’s 6^th Army in Stalingrad by General Polkovnik Andrei I. Eremenko’s Stalingrad Front (General Leytenant Vasili I. Chuikov’s 62^nd Army, General Leytenant Mikhail S. Shumilov’s 64^th Army, General Leytenant Yakov T. Cherevichenko’s 5^th Army and General Major Nikolai I. Trufanov’s 51^st Army) and General Leytenant Konstantin K. Rokossovsky’s Don Front (General Leytenant Pavel I. Batov’s 65^th Army, General Leytenant Ivan V. Galanin’s 24^th Army and General Leytenant Stepan A. Kalinin’s 66^th Army). Stalin codenamed the operation to achieve this end 'Koltso', which was to split the 6^th Army's pocket along a west/east axis and then wipe out the resulting northern and southern parts in succession. The main effort would be the drive through the pocket from the west forces of the Don Front, which was to be allocated the 2^nd Guards Army from the Stavka reserve and be ready to start by 18 December. At the same meeting, Stalin and Vasilevsky decided to strengthen the South-West Front’s left flank in 'Saturn' by adding the 5^th Shock Army.

It was soon realised by the Soviets, however, that their forces in the south were insufficient for two strategic blows at the same time, however, and it was thus decided to postpone 'Saturn' until Stalingrad had been reduced. This thinking was confirmed by the presence of two powerful German groupings (Generaloberst Karl Adolf Hollidt’s Armeeabteilung 'Hollidt' near Tormosin and Generaloberst Hermann Hoth’s Armeegruppe 'Hoth' near Kotelnikovo), which could have taken any Soviet advance in flank as it struck down the Don river. As it was, the Soviet high command decided that while the Don Front (together with the 62^nd and 64^th Armies of the Stalingrad Front) contained the Germans in Stalingrad until the Soviets were ready to crush them, the South-West Front and the rest of the Stalingrad Front should remain poised on the defensive to deal with the inevitable German counter-offensive to relieve Stalingrad, which was planned and executed as 'Wintergewitter' (i).

'Saturn' had not started, and 'Koltso' was not yet ready when von Manstein began his 'Wintergewitter' (i) offensive to break though toward the 6^th Army beleaguered in Stalingrad. Vasilevsky was at the headquarters of the Don Front on the morning of 12 December, according to General Konstantin K. Rokossovsky, and, immediately after receiving the information that 'Wintergewitter' (i) was under way, telephoned Stalin to ask successfully for the 2^nd Guards Army to be transferred to the Stalingrad Front. Vasilevsky’s account says he did not make the request until later in the day and did not get the Stavka’s decision until that night. Whatever its precise timing, the diversion of the 2^nd Guards Army put 'Koltso' into abeyance.

On the night of 13/14 December, according to Vasilevsky, the Stavka made the signally important decision to scale back the size of 'Saturn', though Zhukov’s account says that he, Vasilevsky and the general staff had already decided at the end of November for a smaller 'Saturn', and that at the same time he had also told Stalin to expect a German attack ('Maigewitter') toward the Stalingrad pocket from the Kotelnikovo area.

'Saturn' was now recast as 'Malyi Saturn' (small Saturn) to differentiate it from its predecessor, which retrospectively became 'Bol’shaya Saturn' (great Saturn). Instead of proceeding to the south on the line line Millerovo and Rostov-na-Donu via Kamensk-Shakhtinsky, the right arm of the envelopment was now to be angled to the south-east inside the Don bend, and instead of advancing to the south-west, the left arm was now to drive to the west. The two arms were to meet near Tatsinskaya and Morozovsk. The changes in the axes of advance reduced the projected depth of the Soviet advance by half.

The conversion from 'Bol’shaya Saturn' to 'Malyi Saturn' may also have been, at least in part, a growing note of caution resulting from the course of events elsewhere. The West Front and Kalinin Front had begun 'Mars' during the morning of 25 November and, in its first stage, repeated the pattern at Stalingrad, with massive thrusts from the east and west designed to pinch out the Rzhev salient. However, 'Mars' was opposed by Generaloberst Heinrich-Gottfried von Vietinghoff-Scheel’s (from 1 December Generaloberst Walter Model’s) combat-hardened 9^th Army, and after the 20^th Army, the most important formation of the West Front on the eastern face of the salient, had lost more than half its tanks by committing them piecemeal in trying to obtain a breakthrough, one Panzerkorps handled the defence of that area with ease. The Kalinin Front’s attacks on the west, in the area to the south of Bely and along the Luchesa river, gained more success in advancing to depths of 20 and 10 miles (32 and 16 km) respectively. The 9^th Army began a counter-offensive on 7 December and turned the Soviet break-in to the south of Bely into a pocket, in which the Germans eventually killed 15,000 Soviet troops and took prisoner another 5,000. On 11 December, the West Front launched a second attempt during whose first two days the 9^th Army destroyed 295 Soviet tanks. On 13 and 14 December the pace of 'Mars' slackened appreciable, leaving only the penetration along the Luchesa river to be contested into the new year.