'Nikolaus' was a German undertaking intended to seal the gap between General Walter Weiss’s 2^nd Army and Generalfeldmarschall Walter Model’s 9^th Army of Generalfeldmarschall Ernst Busch’s Heeresgruppe 'Mitte' on the Eastern Front (20/26 December 1943).

On 25 November Busch had ordered the 9^th Army to seal off the Soviet bridgehead at Propoysk, and the 9^th Army and 2^nd Army then to counterattack into the gap between their flanks, close it, and regain control of the railway, which essential to the nourishment of the army group with equipment, weapons, ammunition and all manner of other supplies. The first order could not be executed for the complete lack of the troops with which to make the effort. In their 'Belorussian Strategic Offensive Operation', the Soviets had already torn open a 50-mile (80-km) length of the 'Panther-Stellung' and passed some 18.67 miles (30 km) to the west of it. The most which the 9^th Army could hope to achieve was to slow the Soviet progress.

The armies intended to execute the second order on 30 November, but in the next few days the Soviets advanced to the north-west so rapidly and in such strength that neither army could spare troops for the counterattack. The Oberkommando des Heeres promised Oberst Hans-Ulrich Back’s 16^th Panzerdivision from Italy, but as this single division would not be sufficient for the task demanded, Busch proposed pulling the centre of the 9^th Army back to the Dniepr river to gain two more divisions. Hitler resisted the idea until 30 November, the day on which the troops of General Konstantin Rokossovsky’s Beloruusian Front had reached the Dniepr river to the west of Propoysk and smashed the last remnants of the 'Panther-Stellung' farther to the south.

At the end of November the 2^nd Army had established a new front to the east of Kalinkovichi, albeit some miles to the west of the line which Hitler had ordained, and during the night of 4 December the 9^th Army completed its own retirement. Having improved their positions somewhat, the two armies could prepare the planned counterattack to close the gap between them. On 6 December they issued the orders for this 'Nikolaus' counterattack and, allowing time for the 16^th Panzerdivision to arrive, set 16 December for its start. After 8 December strong attacks on the northern flank of the 2^nd Army tied down all of that army’s reserves, however, and on 14 December a resurgence of fighting in the angle of the Beresina and Dniepr rivers compelled the 9^th Army to ask for the start of 'Nikolaus' to be delayed to 20 December.

That the counterattack began on time on 20 December was itself something of a surprise, and its initial success was greater than anyone had expected. On the second day the spearheads of the 2^nd Army and 9^th Army met at Kobyl’shchina. The army group ordered the divisions to regroup swiftly and turn to the east to clear the railway. Until then neither the army group nor the army commands had expected to do more than close the gap, and they had not been very confident of accomplishing that.

On 22 December the attack continued, gaining ground to the east against stiffening resistance as the Soviets poured in troops from the flanks. In three more days the Germans reached the railway in the north, but in the south were stalled by a strong line on the Ipa river. On 26 December Busch, worried about his northern flank, removed the 16^th Panzerdivision for reallocation to Generaloberst Georg-Hans Reinhardt’s 3^rd Panzerarmee and told Model and Weiss to stop the counterattack and re-establish their armies along a favourable defence line.