Yet beyond the understrength units and questionable leadership, the greatest threat to the viability of Operation Gallop was the woeful state of the Southwest Front’s logistical support, which was still dependent upon railheads on the far side of the Don. Simply put, the Red Army at this point still lacked the support infrastructure to sustain mechanized Deep Operations. Vatutin’s front was extremely short of trucks and thus he had been unable to build up any forward logistic depots to support the offensive. Even with the trucks available, they had great difficulty moving on roads that were often covered with a metre of snow. There were limited numbers of ZIS-42 halftracks based upon the ZIS-5 truck, but their lack of front-wheel drive severely reduced their mobility in snow or mud. Nor could the VVS help much with transport aircraft – in stark contrast to the Luftwaffe’s Ju-52 transports that routinely provided aerial resupply – since the 17 VA supporting the Southwest Front had only a single transport regiment with 20 Li-2 transports (based upon the American-built DC-3). Furthermore, the VVS preferred to use its Li-2s as night bombers instead of bringing up fuel for tank units at the front. Thus, when Popov’s armour drove off into the white snowy wilderness beyond the Donets, they would essentially be out of supply for an extended period.
Nevertheless, Vatutin believed that Operation Gallop, with the Voronezh Front’s Operation Star occurring on its northern flank, would carry the day despite a host of problems. Indeed, Soviet operational planning was driven by post-Stalingrad hubris and an almost French-style attitude that they would muddle through somehow. In the process, any potential German responses were ignored. This style of planning, which omits terrain, weather, logistics and the enemy, begs for disaster.
On the morning of 29 January, General-leytenant Fedor M. Kharitonov’s 6th Army attacked on Vatutin’s right flank with four rifle divisions while General-major Vasiliy I. Kuznetsov’s 1st Guards Army (1 GA) attacked on the left flank with three rifle divisions. In this sector that was over 100km wide, von Manstein had Armee-Abteilung Lanz with the 298. and 320.Infanterie-Divisionen and the 19.Panzer-Division, which only had a small number of operational tanks. The Germans were hopelessly outnumbered in this sector and they elected to conduct a fighting withdrawal which upset Vatutin’s timetable. Vatutin relied on his rifle divisions to conduct the pursuit, enabling his armour to enjoy a few more days of rest, and committed only the 4th Guards Tank Corps to assist the infantry. Although mauled, both German infantry divisions eventually succeeded in retreating across the Donets at Izyum and Zmiyev. The 19.Panzer-Division pulled into a hedgehog north of the Middle Donets at Kremennaya and put up stiff resistance for two days before pulling back across the river. Consequently, the 4th Guards Rifle Corps (4 GRC) of Kuznetsov’s 1GA did not begin crossing the Donets until 1 February. The 6th Guards Rifle Corps, with the 18th Tank Corps in support, crossed the Donets further east near Lysychansk and mounted a fixing attack against the 19.Panzer-Division. Meanwhile, Kharitonov’s 6th Army slowly moved westward against light resistance, but did not capture Izyum until 5 February and did not reach Zmiyev until 10 February.
Ominously, the first elements of the SS-Panzerkorps were already beginning to arrive in the vicinity of Kharkov just as Operations Gallop and Star were commencing and had been detected on the Northern Donets by Soviet scouts. Yet more immediately serious was von Manstein’s successful effort to transfer the bulk of the 1.Panzerarmee from the Rostov area on his right flank to Slavyansk on his left flank, a move he described in chess terms as ‘castling’. Von Funck’s 7.Panzer-Division, with 35 tanks, was the first to arrive at Slavyansk, just as the 4GRC was crossing the Donets to the northwest. Generalleutnant Hermann Breith’s III. Panzerkorps headquarters also established itself in Artemovsk and selected positions for the 3. and 11.Panzer-Divisionen, which were still enroute. Vatutin waited until Kuznetsov’s infantry had moved three rifle divisions across the Middle Donets and established viable bridgeheads before committing Popov’s armour. Poluboyarov’s 4th Guards Tank Corps (4GTC), with 37 tanks, was the first across on 1 February and while 4GRC went to secure Slavyansk, 4GTC brushed past the city and went on to occupy Kramatorsk. However, by the time that the vanguard of 4GRC arrived outside Slavyansk, Panzer-Grenadier-Regiment 7 was firmly established in the town, along with artillery.