How long might the campaigning season in the Caucasus have lasted for the Germans?

The German campaign in the Caucasus had no real 'campaigning season'.

Although typically the Soviet defenders were better equipped for the seasons earlier, the German troops adapted quickly as well. As can be seen from the dates of fighting, the contest lasted through all the beginning of winter. While in the mountains the conditions of 'fall season' start early, the lowest temperatures on the Northern Hemisphere aren't reached before January, often February. By then, the Germans were already well beaten.

Conditions on the ground were difficult for both sides, but it was less 'the weather' to blame for the German defeat.

_{Alex Buchner: "Vom Eismeer bis zum Kaukasus. Die deutsche Gebirgstruppe im Zweiten Weltkrieg 1941/42", Dörfler Zeitgeschichte, 1988}

Strategy and tactics weren't matched for a difficult, if not untenable, position. Supply lines were not the only thing that was quite over-extended, strategical reach was as well and the planning was a mess.

However, what seemed simple in map exercises proved far more difficult to execute in the field. Heeresgruppe A did succeed in invading the Caucasus in July and quickly routed the armies of the North Caucasus Front. While Kleist’s Panzers captured Maikop on 10 August and pushed south towards Grozny, Ruoff overran the Kuban. In the skies, the Fliegerkorps IV gained local air superiority to support the ground offensive. Yet just when Heeresgruppe A appeared to be on the cusp of victory, Hitler began tinkering with the basic plan: he started transferring forces from the Caucasus to reinforce Heeresgruppe B’s faltering advance towards the Volga. He also failed to transfer three promised divisions of the Italian Alpine Corps to the Caucasus, where they were desperately needed to help clear the Black Sea coast. By October, Operation Edelweiss had run out of steam short of its primary objectives due to increased Soviet resistance and German logistic problems. Ruoff’s 17.Armee failed to capture the ports of Tuapse or Sukhumi, despite repeated efforts, and Kleist’s 1.Panzerarmee was stopped short of Grozny. One final German push in early November resulted in the near destruction of 13.Panzer-Division when it was briefly encircled.

For a brief period, the front lines in the Caucasus stabilized and both sides shifted to the defensive. In late November, General der Kavallerie Eberhard von Mackensen took command of 1.Panzerarmee while von Kleist moved up to take command of Heeresgruppe A. This brief period of stasis ended when the Soviet South-West and Stalingrad fronts launched a major counter-offensive, Operation Uranus, on 19 November 1942. Four days later, the German 6.Armee and part of 4.Panzerarmee in Stalingrad were cut off and faced with destruction. In desperation, the Oberkommando des Heeres (OKH) immediately cobbled together a rescue plan known as Operation Wintergewitter, which entailed von Mackensen’s 1.Panzerarmee transferring the 23.Panzer-Division and the SS-Panzergrenadier Division Wiking to Generaloberst Hermann Hoth’s 4.Panzerarmee. Much of Fliegerkorps IV was also transferred northwards, which immediately gave the Soviet 4th and 5th Air Armies air superiority in the Caucasus.

Heeresgruppe A’s position in the Caucasus was quite tenuous and became even worse when Operation Wintergewitter failed in mid-December and the Stalingrad Front (renamed the Southern Front on 1 January 1943) began advancing south. It soon became obvious to both sides that Heeresgruppe A might become isolated in the Caucasus; if that occurred, the entire German southern front in Russia would collapse. Yet Hitler was extremely reluctant to abandon his position in the Caucasus and did not authorize a retreat until 29 December; even then, 1.Panzerarmee was only authorized to retreat 100km from the Terek to the Kuma River line. Hitler optimistically believed that the Kuma position could be held until spring 1943, when he could then mount a new offensive towards the Caucasus oilfields. By holding further south, Hitler also hoped to retain the captured oilfields around Maikop, which had just been repaired.

At the end of 1942, Soviet forces in the Caucasus consisted of two main groupings. General-polkovnik Ivan I. Maslennikov’s Northern Group of Forces, in the Grozny and Terek River sector, consisted of four armies (9th, 37th, 44th and 58th) and two independent cavalry corps supported by the 4th Air Army (Vozdushnaya Armiya – VA). In the Tuapse sector, General Ivan E. Petrov’s Black Sea Group consisted of four armies (18th, 46th, 47th and 56th) supported by the 5th Air Army and the Black Sea Fleet’s naval air arm (VVS-ChF). The Transcaucasus Front served as a force provider and logistical source for both groups, but did not directly command units in the field.

For the Soviets, the Caucasus was a backwater theatre and received far less material support than was going to the main effort in the Stalingrad sector. Nevertheless, Stavka (the Soviet High Command) expected the forces in the Caucasus to drive Heeresgruppe A from the region at the earliest opportunity.

On 1 January 1943, von Mackensen’s 1.Panzerarmee began its retreat from the Terek River and Maslennikov’s four armies immediately launched their long-planned counter-offensive. Maslennikov’s pursuit, spearheaded by two cavalry corps and two ad hoc mechanized groups, was poorly coordinated but managed to keep 1.Panzerarmee on the run and prevent it from forming a viable line on the Kuma River. By 10 January, Maslennikov’s spearheads were across the Kuma in force. Even worse for 1.Panzerarmee, the Southern Front pushed Hoth’s forces back over 100km and was approaching the Manych River, which threatened to envelop von Mackensen’s open left flank. If Soviet armour crossed the river, there would be little to stop it from severing von Mackensen’s line of communications and cutting off the bulk of Heeresgruppe A in the Caucasus. Amazingly, Hoth managed to fight a two-week delaying operation on the Manych River, which bought time for von Mackensen’s 1.Panzerarmee to escape the Soviet pincers. Overall, the German retreat from the Caucasus was fairly well managed but still something of a disaster since inadequate fuel supplies caused hundreds of vehicles to be abandoned.

Ruoff’s 17.Armee was also forced to retreat, which was complicated by the dispersed nature of its forces. The V Armeekorps and the Romanian Cavalry Corps near Novorossiysk were ordered to stand fast, but XXXXIV Armeekorps in the mountains east of Tuapse and XXXXIX Gebirgskorps spread through the mountains north and east of Sukhumi were faced with a daunting retreat through high mountains in winter. All four divisions of the XXXXIV Armeekorps were forced to retreat along the single-track Tuapse–Maikop road, little more than a muddy track, causing great congestion. About half the German artillery and a great deal of ammunition were abandoned during the retreat.

Although Petrov’s Black Sea Group was itself short on supplies, Stavka insisted that it begin a counter-offensive against the retreating 17.Armee as soon as possible. (There was no rail link to the Tuapse sector, so the Black Sea Group had been dependent upon supply by sea for the past six months.) While Petrov favoured a methodical advance over the rough terrain, Marshal Georgy K. Zhukov unrealistically demanded that Petrov mount an all-out offensive to break through to Krasnodar. Petrov dutifully developed a two-phase offensive plan, which he called Operation More (Sea) and Operation Gory (Mountains). The first phase began on 12 January 1943 when General-leytenant Fedor V. Kamkov’s 47th Army attacked the Romanian Cavalry Corps sector near Krymskaya with two rifle divisions and three brigades. The Romanian 3rd Mountain Division and 9th Infantry Division, holding prepared positions, easily repulsed this inadequate attack and Kamkov was soon relieved of command. Operation More was supposed to include an amphibious landing near Novorossiysk, but this was deferred.

Petrov waited a bit longer before implementing Operation Gory, but under pressure from Stavka, General-major Andrei A. Grechko’s 56th Army began attacking with four rifle divisions in the Severskaya sector, 35km south of Krasnodar, on 16 January 1943. The Romanian 9th Cavalry Division held a 42km-wide front in this sector. With a 5:1 numerical edge in manpower, Grechko’s 56th Army was able to surround several Romanian battalions and advanced 10–12km in two days. If Grechko could reach Krasnodar – which was only lightly defended – a good portion of 17.Armee would be isolated. However, persistent rain made tactical mobility difficult in the snow-covered mountains, which gave General der Artillerie Maximilian de Angelis’ XXXXIV Armeekorps just enough time to respond to the crisis. Generalleutnant Ernst Rupp’s 97.Jäger-Division hurriedly dispatched three battalions to reinforce the Romanian cavalry and German counterattacks on 17–18 January caught Grechko’s troops by surprise. Tough infantry combat followed for several days as Rupp’s division gradually slowed the 56th Army’s advance, assisted by the German 125.Infanterie-Division on one flank and the Slovak 1st (Mobile) Division, which held Goryachy Klyuch. Thanks to Rupp’s delaying actions, de Angelis’ XXXXIV Armeekorps succeeded in retreating to Krasnodar.

_{Robert Forczyk: "The Kuban 1943. The Wehrmacht’s last stand in the Caucasus", Campaign 138, Osprey: Oxford, New York, 2018.}

More detail for the Operation Edelweiss itself in

The Caucasus was the kind of campaign that the panzer divisions were designed to win, using bold manoeuvres across flat steppes against a disorganised foe that lacked proper air, artillery or armour support. However, Hitler and the OKH failed to provide their main effort with the logistic resources and air support it needed to succeed. Had 1. Panzerarmee received priority of fuel in August, including deliveries of fuel by air, it almost certainly could have ‘bounced’ the Terek before the Soviets could build a defensive line along the entire river. Reduced to only two fuel-starved divisions at the tip of his spear, von Kleist’s spearhead was stopped more by his own side than the Red Army. Failing this, Hitler should have recognised by mid-September 1942 that the offensive in the Caucasus was futile and shifted all effort to Heeresgruppe B – which could have reduced the risk to 6. Armee at Stalingrad. Historians have generally focused on Stalingrad as the defining moment of the 1942 campaign, but the faulty German performance in the Caucasus indicates endemic problems in the Third Reich’s style of operational and strategic planning that go well beyond the mistakes of a few individual generals.

Under the circumstances, the Red Army’s performance in the Caucasus was quite good and after the pell-mell retreat of the first few weeks, they made the Germans pay dearly for terrain. The Soviet stand along the Terek River and at Ordzhonikidze was a great defensive success, followed up by constant counterattacks that gradually unravelled the overextended Heeresgruppe A. The main Soviet problem in the Caucasus campaign was a tendency by Stalin to put unqualified NKVD generals like Maslennikov or party commissars like Lazar M. Kaganovich in key decision-making positions; the reason the Red Army performed well in the Caucasus was because it had fighting generals like Koroteev and Kirichenko. Finally, it is worth noting that both sides conducted concurrent air, ground and sea operations during the campaign that affected the outcome – which was rare on the Eastern Front. In modern parlance, the Caucasus was a joint campaign, conducted by all three services, plus a sprinkling of Axis coalition partners. Success on the ground proved heavily dependent upon local air superiority and naval forces also played a significant role at key moments.
_{Robert Forczyk: "The Caucasus 1942–43. Kleist’s race for oil", Campaign 281, Osprey: Oxford, New York, 2015.}