This was the Soviet undertaking, also known as the 'Goldap-Gumbinnen Offensive Operation', by General Ivan D. Chernyakhovsky’s 3rd Belorussian Front to penetrate the borders of East Prussia, which was held by elements of Generaloberst Hans-Georg Reinhardt’s Heeresgruppe 'Mitte' (16/30 October 1944).
A failure largely as a result of strong German resistance, the operation had been planned to capitalise on the success of the 'Memel Offensive Operation' farther to the north. The 405,000 troops of the General Hovhannes Kh. Bagramyan’s 1st Baltic Front and the 3rd Belorussian Front had succeeded in pushing Generaloberst Erhard Raus’s 3rd Panzerarmee back to the East Prussian border, surrounding the city of Memel and reaching the shore of the Curonian Lagoon. The Stavka now permitted Chernyakhovsky to exploit this success further by attacking along the axis linking Gumbinnen and Königsberg via Insterburg deep into East Prussia.
Chernyakhovsky’s plan involved using General Polkovnik Nikolai I. Krylov’s 5th Army and General Polkovnik Kuzma N. Galitsky’s 11th Guards Army (35 infantry divisions and two tank corps) to break open the German defences so that the forces of General Major Aleksei S. Burdeinyi’s II Guards Tank Corps and General Leytenant Aleksandr A. Luchinsky’s 28th Army could be released for the exploitation. General Leytenant Piotr G. Shafranov’s 31st Army and General Leytenant Ivan I. Lyudnikov’s 39th Army would advance on the flanks of the main force. The opposing German forces, from General Friedrich Hossbach’s 4th Army (15 infantry divisions and two cavalry brigades), were aided by the presence of major fortifications, and had been heavily reinforced from the German general reserve and elements of Raus’s 3rd Panzerarmee.
In overall terms, Reinhardt’s Heeresgruppe 'Mitte' had the southern part of the 3rd Panzerarmee (General Sigfrid Henrici’s XL Panzerkorps and General Rolf Wuthmann’s IX Corps) and the northern part of the 4th Army (General Maximilian Felzmann’s XXVII Corps, General Helmuth Weidling’s XLI Panzerkorps, Generalleutnant Wilhelm Schmalz’s Fallschirmpanzerkorps 'Hermann Göring' and General Horst Grossmann’s VI Corps).
On 16 October, the 5th Army and 11th Guards Army went onto the offensive and initially penetrated some 6.8 miles (11 km) into the German defensive belt. The flanking armies moved into action during the following day, by which time units of the 11th Guards Army had crossed the East Prussian border. The Soviet troops ran into extremely strong resistance, however. It took them four days to penetrate the Germans' initial tactical defence line, while the second defence line was so strong that Chernyakhovsky was compelled to commit the II Guards Tank Corps to break it, and the Soviet casualties were again very heavy. On 20 October, the German second line was broken by the 11th Guards Army and II Guards Tank Corps, to the east of Gumbinnen, which was defended by the guns of Generalmajor Günther Sachs’s 18th Flakdivision and the Fallschirmpanzerkorps 'Hermann Göring', which had been redeployed in the area to counter the Soviet advance. On 21 October, the Soviets committed their reserve, the 28th Army, but the offensive in the north was fought to a standstill in the region of Stalluponen by some effective German counterattacks.
The Soviet forces had taken Gumbinnen by 22 October, but the town was retaken by the Germans on 24 October after they had committed Generalmajor Rolf Lippert’s 5th Panzerdivision and the 505th schwere Panzerabteilung, the latter equipped with PzKpfw VI Tiger II heavy tanks. Units of 11th Guards Army found themselves cut off in the area of Grosswaltersdorf, and were involved in intense fighting.
In the meantime, the Germans had pressed more reserves, including Oberst Zimmermann’s 102nd Panzerbrigade and Oberst Hans-Joachim Kahler’s Führer Grenadierbrigade, into counterattacks at Goldap, on the southern sector of the Soviet penetration, and retook the town on 25 October. The Soviet attacks continued until 27 October, as the flanking armies sought to close up to the 11th Guards Army.
There was more fighting in the immediate aftermath of the offensive’s end on 27 October: on 28 October, the 31st Army retook Goldap in a surprise attack, but the town was again recaptured by the 5th Panzerdivision, which had been redeployed from the Gumbinnen area, on 3 November.
The Soviet losses were in the order of 16,820 dead and 62,710 wounded, but the German losses remain unknown.