The 'East Prussian Strategic Offensive Operation' was a Soviet strategic offensive in the northern sector of the Eastern Front, with some German units not surrendering until 9 May (13 January/25 April 1945).

A major battle within the operation was that for Königsberg (now Kaliningrad), and the operation is known to German historians as the 2^nd East Prussian Offensive, the 1^st East Prussian Offensive (known to the Soviets as the 'Goldap-Gumbinnen Operation') having been implemented on 16/27 October 1944 by General Ivan D. Chernyakhovsky’s (from 20 February 1945 Marshal Aleksander M. Vasilevsky’s) 3^rd Belorussian Front as part of the 'Memel Offensive Operation' of General Hovhannes Kh. Bagramyan’s 1^st Baltic Front.

While the main Soviet effort at this time was the 'Vistula-Oder Strategic Offensive Operation' launched on 12 January by the 1^st Belorussian Front and 2^nd Ukrainian Front to drive primarily to the west, the 'East Prussian Strategic Offensive Operation' was launched one day later. This latter was to push, from the line between Warsaw and the Niemen river, in a huge pincer operation. While the southern arm of this pincer advanced to the north-west in an effort to reach the coast of the Baltic Sea in the area of Elbing, between Braunsberg and Heiligenbeil, the northern arm was to drive basically to the west in in order to reach the Baltic Sea between Königsberg and Memel. This was designed to separate East Prussia from the rest of Germany in the south and from the great German pocket in the Kurland peninsula in the north, and in the process destroy Generaloberst Georg-Hans Reinhardt’s Heeresgruppe 'Mitte'.

The 'East Prussian Strategic Offensive Operation' was undertaken in a number of operational-level sub-operations. These were the 'Insterburg-Königsberg Offensive Operation' (14/26 January), the 'Milau-Elbing Offensive Operation' (14/26 January), the 'Rastenburg-Heilsberg Offensive Operation' (27 January/12 February), the 'Braunsberg Offensive Operation' (13/22 March), the 'Königsberg Offensive Operation' (6/9 April) and the 'Samland Offensive Operation' (13/25 April).

In East Prussia, Heeresgruppe 'Mitte' was already in a position of the utmost danger. The army group’s primary assets were General Walter Weiss’s 2^nd Army in the south facing Marshal Sovetskogo Soyuza Konstantin K. Rokossovsky’s 2^nd Belorussian Front, General Friedrich Hossbach’s 4^th Army in the centre facing the right wing of the 2^nd Belorussian Front and the left wing of General Ivan D. Chernyakovsky’s 3^rd Belorussian Front, and Generaloberst Erhard Raus’s 3^rd Panzerarmee in the north facing the right wing of the 3^rd Belorussian Front and the left wing of General Hovhannes Kh. Bagramyan’s 1^st Baltic Front.

Facing 14 Soviet armies with a strength of almost 1.67 million men, Reinhardt’s three armies totalled 580,000 men excluding a motley assortment of about 200,000 personnel of the Volkssturm (national militia) and police. Reinhardt had unsuccessfully asked Adolf Hitler to allow the evacuation of Kurland and the withdrawal of the 4^th Army, which was stretched out to the south-east in a salient toward Suwałki and Augustów back to the chain of the Masurian Lakes near Lötzen. On the other hand, the Soviet armies had a mobility and the superiority of strength which made it feasible for them to attack in both the north and the south, with the Masurian Lakes between them, in two great pincer movements directed on Königsberg and Marienburg with the objective of enveloping the whole of East Prussia.

However, despite their abundance of equipment and very strong tank and artillery forces, the Soviet forces were weakened by their customary shortage of infantry as a result, as always, of the high level of infantry casualties in preceding operations. For this reason, at this time Rokossovsky’s 2^nd Belorussian Front received 120,000 replacement personnel, but none of these came from the Soviet home reinforcement organisation. Just under 40,000 of the replacements were wounded and sick returned to duty; 20,000 others were men combed out of the rear and supply services; 10,000 were former Soviet prisoners recaptured from the German; and 53,000 were fresh conscripts, primarily from the recaptured areas of Poland, Ukraine and the Baltic states, forced into the Soviet army with little or no training, and in most cases even less commitment to the Soviet cause.

The Soviet plan was for Rokossovsky’s 2^nd Belorussian Front 1 to attack to the north and north-west from its Narew bridgehead. The main thrust was to be made almost directly to the north against the 2^nd Army at Mława, Deutsch-Eylau, Osterode and Marienburg by four armies and one tank army, with one army in reserve. Two other armies and one tank corps were to make subsidiary thrusts on a north-westerly axis toward Thorn and Pomerania.

Farther to the north, Chernyakhovsky’s 3^rd Belorussian Front 2 was to attack to the west into East Prussia against the 3^rd Panzerarmee, moving along the line of the Pregel river to Königsberg, thereby cutting off the German troops in Memelland. Four armies and two tank corps were to be used in the main sector of the attack, and General Leytenant Afanasi P. Beloborodov’s 43^rd Army of the 1^st Baltic Front was to support the north flank by attacking across the Niemen river.

Five lines of ammunition were allotted to the attack, two of which were to be used on the first day of the fighting.

Rokossovsky’s offensive began on 13/14 January amid heavy snow which cut the visibility to only 200 yards (185 m), the forward battalions attacking with such success that the artillery fire programme was cancelled. In the first few hours the level of German resistance was insignificant, but gradually there began to emerge counterattacks in company and battalion strength, and the Germans started to fight with a determination which the Soviets found reminiscent of the earlier days of the war. Nevertheless, the Soviet forces made steady progress, though only at the cost of very high casualties as the defence had the advantage of substantial fortifications in the Insterburg Gap to the east of Königsberg, and around Heilsberg. On 15 January Reinhardt committed his army group reserves, Generalleutnant Dr Karl Mauss’s 7^th Panzerdivision, under the temporary command of Oberst Max Lemke, and Generalmajor Karl Lorenz’s Panzergrenadierdivision 'Grossdeutschland', and these inflicted losses and delays on the 2^nd Belorussian Front.

During the first days of the Soviet offensive the 3^rd Panzerarmee was largely destroyed or withdrew into Königsberg, while Hossbach’s 4^th Army began to find itself outflanked.

Rokossovsky had committed his forces across the Narew river on 14 January in an advance to the north-west, but on 20 January was ordered to swing the axis of his advance to the north in the direction of Elbing, a sudden change of direction which caught both Reinhardt and Hossbach by surprise.

It was at this time, however, that Hitler removed General Dietrich von Saucken’s Panzerkorps 'Grossdeutschland' from Reinhardt’s command and despatched it by rail to strengthen Generaloberst Josef Harpe’s (from 17 January Generalfeldmarschall Ferdinand Schörner’s Heeresgruppe 'A' at Łódź in an effort to stem the offensive of Marshal Sovetskogo Soyuza Georgi K. Zhukov’s 1^st Belorussian Front farther to the south, and after Rokossovsky had committed another two tank corps against Reinhardt, this added strength was instrumental in getting the Soviet offensive under way once more.

On that day the weather became fine everywhere and the tactical warplanes of General Polkovnik Konstantin A. Vershinin’s 4^th Air Army was able to fly 2,500 sorties. The two towns of Mława and Modlin, which Hitler had designated as fortresses to be held at all costs, were taken, and by 19 January Rokossovsky had broken through on a 70-mile (115-km) front to a maximum depth of 40 miles (65 km). On the same day Soviet troops crossed the pre-war East Prussian frontier from the south near Neidenburg with the 2^nd Army retiring before them, abandoning depots and supplies and mining the roads as it went. Tannenberg was taken on 21 January, before they withdrew removing the remains of Generalfeldmarschall Paul von Hindenburg and his wife and destroying the great memorial to this German leader of World War I and post-war president.

On Rokossovsky’s right flank, General Leytenant Nikolai S. Oslikovsky’s III Guards Cavalry Corps captured the major town of Allenstein on 22 January, threatening the rear of the 4^th Army. By 24 January Rokossovsky’s leading armoured formations had reached the shore of the Vistula Lagoon, severing the land communications with the rest of German armed forces for the entire 4^th Army along with several divisions of the 2^nd Army, which were now trapped in a pocket centred on East Prussia.

Farther to the north, Chernyakhovsky’s 3^rd Belorussian Front had moved due west into East Prussia, attacking Raus’s 3^rd Panzerarmee on 13 January, using the fog, low cloud and the noise of low-level aircraft to conceal the presence of the forces being concentrated for the attack. The attack began at 06.00, but despite the weight of supporting air and artillery fire the Soviet progress was very slow. Schlossberg and Kattenau changed hands several times in the fighting, but the Soviets took Tilsit on 18 January. Although it was under great pressure, the 3^rd Panzerarmee continued to present an unbroken front.

Hossbach’s 4^th Army in the exposed salient between Goldap in the north and the Narew river in the south, forward of the Masurian Lakes, had not yet come under attack, but Weiss’s 2^nd Army in front of Rokossovsky’s 2^nd Belorussian Front was by now in acute danger of disintegration. Although reinforced by sailors, Luftwaffe ground personnel and Volkssturm, many Germans fled and many other surrendered. When surrounded, some strongpoints refused to continue the fight, and some of these garrisons' commanders were to be shot out of hand for their failure.

On the evening of 23 January a detachment of Major General Ksenofont M. Malakhov’s XXIX Tank Corps of Volsky’s 5^th Guards Tank Army reached Elbing near the Baltic, the Germans having been so slow to react to this deep drive that the town’s shops were still open and the factories were still at work as the tanks drove down the main street with their headlights on. Toruń (German Thorn) and Marienburg were also taken, and by 26 January the 3^rd Panzerarmee, 4^th Army and part of the 2^nd Army had been cut off in East Prussia after Rokossovsky’s armies had advanced 125 miles (200 km) in 12 days.

Reinhardt had pressed for the early withdrawal of the 4^th Army to positions behind the Masurian Lakes, but it was not until 21 January that Hitler had belatedly acceded to the army group commander’s request. By then it was necessary for the 4^th Army to form a new front to the rear of 3^rd Panzerarmee near Wormditt, but facing to the west in order to cover the gap caused by the breaking of the 2^nd Army. On 22 January Hitler further agreed to the evacuation of Memel, but the following day he was insisting that the Lötzen line in the Masurian Lakes was to be held at all costs. This position had already been outflanked by the Soviet advance, however, and Reinhardt was convinced that he should withdraw, taking with him as much as possible of the East Prussian population in a bid to rejoin the German positions on the Vistula and Nogat to the west of Danzig. Hossbach, commander of 4^th Army, shared Reinhardt’s opinion and retired on Heilsberg behind the Masurian Lakes in preparation for mounting an attack to the west.

Chernyakhovsky had meanwhile succeeded in rolling up the German defences from the east, pushing the remnants of the 3^rd Panzerarmee into Königsberg and Samland. On 28 January Bagramyan’s forces captured Memel, the remnants of the three German divisions defending the town being evacuated by sea and redeployed in Samland to reinforce the defence there. With the remnants of Heeresgruppe 'Mitte' contained, the Soviet forces could be concentrated for the reduction of the German forces in Pomerania and the elimination of any possible threat northern flank of their eventual advance on Berlin.

On 26 January a suspicious Hitler began to rage against Reinhardt and Hossbach, ordering their removal, Reinhardt being replaced by Generaloberst Dr Lothar Rendulic from Heeresgruppe 'Nord' and Hossbach by General Friedrich-Wilhelm Müller from the XLVIII Corps of the 2^nd Panzerarmee in the Balkans. Rendulic was expressly ordered to hold Königsberg, the capital of East Prussian, to the bitter end.

On the same day Hitler instigated another reorganisation and a further redesignation of formations, Heeresgruppe 'Nord' becoming Heeresgruppe 'Kurland', Heeresgruppe 'Mitte' becoming a new Heeresgruppe 'Nord', and Heeresgruppe 'A' becoming a new Heeresgruppe 'Mitte'. A new Heeresgruppe 'Weichsel' had been formed to cover Danzig and Pomerania, and under the last’s command were Weiss’s 2^nd Army, General Theodor Busse’s 9^th Army comprising mostly parts of formations and detachments, and supplemented from 2 February by Steiner’s 11^th SS Oanzerarmee. Command of Heeresgruppe 'Weichsel' was entrusted to Reichsführer-SS Heinrich Himmler, who was already the head of the SS, head of the German police and commander of the Ersatzheer, as Hitler was sure that loyalty, reliability and fanaticism were more important than military ability and experience, of which Himmler was totally devoid.

As Heeresgruppe 'Kurland' (26 divisions) and Heeresgruppe 'Nord' (27 divisions) had already been cut off from the rest of the dwindling German empire, the defence in the east was now to depend on Heeresgruppe 'Weichsel', which was to cover the approaches to northern Germany, and Heeresgruppe 'Mitte', which was to cover the approaches to Saxony, the Sudetenland and the whole of what had been Czechoslovakia. General Otto Wöhler’s Heeresgruppe 'Süd' was still in Hungary, and German troops continued to hold most of Yugoslavia and northern Italy. Hitler still considered that the strategic areas most important for the survival of Germany were the oil districts of Hungary, the Vienna basin and the deep-water U-boat training grounds in the Gulf of Danzig.

Thus the battle for East Prussia was almost at an end, although Rendulic was to hold on grimly to the city of Königsberg, Samland and part of the south bank of Frisches Haff for some months to come.

Chernyakhovsky’s forces were now besieging the German forces three pockets: some 15 divisions of the 4^th Army were encircled on the shore of the Vistula Lagoon in what became known as the Heiligenbeil pocket and, after bitter fighting, were finally overcome on 29 March; the remnants of the 3^rd Panzerarmee, now under command of the 4^th Army, became isolated in the siege of Königsberg, which was taken by the Soviets, after massive casualties on both sides, on 9 April, whereupon the remaining German forces around the Bight of Danzig were reorganised into the Armee 'Ostpreussen' under the command of von Saucken; and the third group of German forces, General Hans Gollnick’s XXVIII Corps (otherwise the Armeeabteilung 'Samland') occupied the Samland peninsula, at whose south-western tip the port of Pillau was retained as the last effective evacuation point for the area before its reduction by the Soviets on 25 April in the 'Zemland Offensive Operation'.

Even after this time German forces continued to resist on the Frische Nehrung, the long sandbar enclosing the Vistula Lagoon, until the end of the war.

The German losses in the Soviet 'East Prussian Strategic Offensive Operation' had been 151,757 (including 63,774 irrecoverable) up to 10 February, while the Soviet casualties were 584,778 (including 126,464 irrecoverable) for the whole offensive.