The 'Braunsberg Offensive Operation' was the Soviet fourth of the six sub-operations together constituting the 'East Prussian Strategic Offensive Operation' leading to the almost complete destruction of General Friedrich Hossbach’s 4^th Army in the 'Battle of the Heiligenbeil Pocket' (13/22 March 1945).

The other sub-operations 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 'Königsberg Offensive Operation' (6/9 April) and the 'Samland Offensive Operation' (13/25 April).

The 'East Prussian Strategic Offensive Operation' began on 13 January 1945 with the object of rolling up the substantial German forces in East Prussia and cutting off Königsberg (now Kaliningrad), the provincial capital. The Soviet forces were opposed by Generaloberst Georg-Hans Reinhardt’s Heeresgruppe 'Mitte', which comprised Generaloberst Walter Weiss’s 2^nd Army, Hossbach’s 4^th Army and Generaloberst Erhard Raus’s 3^rd Panzerarmee.

While General Andrei I. Eremenko’s (from 20 February Marshal Sovetskogo Soyuza Aleksandr M. Vasilevsky’s) 3^rd Belorussian Front initially met strong resistance, the outnumbered German forces soon began to suffer serious ammunition shortages, and while Reinhardt warned of the acute nature of the situation as early as 19 January, Adolf Hitler steadfastly refused to authorise the phased withdrawal which was so manifestly required by the operational situation.

To save his formations and units from encirclement, Hossbach started to pull the 4^th Army's formations 1 back to the west in direct contravention of his orders, thereby abandoning the prepared defences around Lötzen on 23 January. By this time, Marshal Sovetskogo Soyuza Konstantin K. Rokossovsky’s 2^nd Belorussian Front had already broken through on Hossbach’s right, and General Polkovnik Vasili T. Volsky’s 5^th Guards Tank Army headed for the Baltic coast, isolating most of East Prussia.

Undertaking a prodigiously difficult series of forced marches in atrocious winter weather, and accompanied by thousands of civilians, the the 4^th Army moved toward the port city of Elbing on the Baltic Sea coast, still held by the 2^nd Army, but found its path blocked by the Soviet 48^th Army to the east of the city. An attack beginning on the night of 26 January initially resulted in the leading units of Generalmajor Ernst König' 28^th Jägerdivision breaking through to Elbing, where it joined forces with they linked up with Generalleutnant Dr Karl Mauss’s 7^th Panzerdivision, but the German forces were then driven back during the next four days after the 48^th Army had regrouped. Hossbach’s formations and units now found themselves pushed into a Kessel (pocket) with their backs to the Frisches Haff.

Hossbach was relieved of his command on 29 January and replaced by General Friedrich-Wilhelm Müller. The army’s corps, now reduced to three in number, were given an order to end their attempt to break-out on 30 January and, together with some of the 2^nd Army's formations and units, found themselves encircled in the area of Heiligenbeil and Braunsberg; many of the civilians trapped with them attempted to escape across the frozen Haff to the Frische Nehrung and thence to Pillau or Danzig, reinforced paths marked by lamps having been constructed across the ice by the 4^th Army's engineers.

As the Nazi leadership had effectively forbidden any evacuation of East Prussia’s civil population, the start of the Soviet attack on 12 January triggered a mass flight to the west in the direction of the coast of the Baltic Sea, and in this flight large numbers of civilians were killed by the Soviets and the severity of the weather. Along the coast, and especially in Pillau, the German navy managed to evacuate many thousands of civilians along the Baltic Sea, and also encouraged a determined land resistance any any delay of the Soviet advance bought time for the evacuation of more civilians.

Soviet attempts to break through the German perimeter early in February were fought off, the 4^th Army being aided by heavy gunfire support from the German heavy cruisers (ex-'pocket battleships') Admiral Scheer and Lützow firing across the Haff from the Baltic sea into the Frauenburg end of the pocket. Frauenburg itself fell to the Soviets on 9 February in fierce fighting involving elements of Generalmajor Franz Griesbach’s 170^th Division, and in the course of one Soviet attack the 3^rd Belorussian Front’s commander, General Ivan D. Chernyakhovsky, was killed near Mehlsack on 18 February by a shell splinter. He was succeeded on 19 February by Vasilevsky who, having contained the rest of Heeresgruppe 'Mitte', concentrated on assembling reinforcements over the next month. Under the supervision of Generalmajor Karl Henke, commander of the German landing forces, the Germans continued resupply and evacuation missions along the Frische Nehrung, often at night to avoid air attack. A long but narrow corridor through to the besieged garrison of Königsberg was also maintained against the attacks of General Polkovnik Kuzma N. Galitsky’s 11^th Guards Army through the combined efforts of Königsberg’s garrison and Generalmajor Hellmuth Mäder 's Panzergrenadierdivision 'Grossdeutschland'.

Though there was no hope of victory, and they were acutely short of men, ammunition, fuel and all other types of supplies, the German forces in East Prussia maintained their determined resistance, in the process inflicting more than 584,790 casualties on the Soviets during the 'East Prussian Strategic Offensive Operation'. Extemporised Kampfgruppen were often bolstered by civilians impressed into the Volkssturm, and many East Prussian villages and towns had been turned into fortified strongpoints, while substantial fortifications had turned Heilsberg into a major centre of resistance. The fighting was prolonged in order to keep open the escape routes for civilians, as noted above, and because requests for the evacuation of the main body of the 4^th Army were rejected by the German high command.

The Soviet forces committed round the pocket were Rokossovsky’s 2^nd Belorussian Front (5^th Guards Tank Army, 3^rd Army, 48^th Army and 50^th Army), and Vasilevsky’s 3^rd Belorussian Front (28^th Army and 31^st Army).

The German forces of the 4^th Army which were caught in the Kessel were Grossmann’s VI Corps (24^th Panzerdivision, 102^nd Division and 349^th Volksgrenadierdivision), General Rudolf Freiherr von Roman’s XX Corps (14^th Division, 21^st Division, 56^th Division, 131^st Division, 292^nd Division and 61^st Volksgrenadierdivision), and Weidling’s XLI Panzerkorps (Fallschirmpanzergrenadier Division 2 'Hermann Göring', Panzergrenadierdivision 'Grossdeutschland', 50^th Division, 170^th Division, 28^th Jägerdivision and 562^nd Volksgrenadierdivision). Almost all of the German formations and units were well below strength even at the start of the 'East Prussian Strategic Offensive Operation', and some additional units involved (such as the 18^th Panzergrenadierdivision and 299^th Division) were destroyed, disbanded or completely evacuated before the collapse of the Kessel.

The German pocket was finally destroyed in the 'Braunsberg Offensive Operation' between 13 and 29 March, in preparation for the 'Königsberg Offensive Operation' (6/9 April).

The Soviets acted with speed to sever all communication between the Kessel and Königsberg as their troops reached the coast, about 5 miles (8 km) from the city on 15 March. The Soviets forced a crossing of the Frisching river in an attack during the night of 17/18 March, further rolling up German defences of the Kessel from the east, and the arrival of better flying weather from 18 March made it possible for the Soviet air forces to undertake an intense aerial bombardment of the 4^th Army's positions.

With almost all communications cut, the German forces in the pocket faced the prospect of either death or being taken prisoner. Some higher-grade formations, such as Oberst Georg Seegers’s, then Oberst Helmut Hufenbach’s and finally Generalmajor Erich Walther’s Fallschirmpanzergrenadier Division 2 'Hermann Göring' and Generalmajor Gustav-Adolf von Nostitz-Wallwitz’s 24^th Panzerdivision, were evacuated by sea, but others were steadily divided into a series of small pockets along the coast. Reports indicated that many German formations and units were now drastically reduced: Generalmajor Georg Haus’s 50^th Division, for example, was down to the equivalent of just one regiment, and even this was incomplete.

The Soviets took Braunsberg on 20 March, and Heiligenbeil, which covered the landward approach to the small port of Rosenberg, was attacked with incendiary bombs on 22 March and stormed on 25 March, the town being almost wholly destroyed. Rosenberg was taken on 26 March, after which the remnants of the 4^th Army withdrew onto the Kahlholzer Haken peninsula, where the perimeter was defended by men of General Georg Jauer’s Panzerkorps 'Grossdeutschland' and the 28^th Jägerdivision. The last evacuations took place on the morning of 29 March from Kahlholz and Balga, where the last remnant of Oberst Helmuth Hufenbach’s 562^nd Volksgrenadierdivision was destroyed while serving as the rearguard.

The Soviets claimed 93,000 German dead and 46,448 taken prisoner during the operation, while the Germans claimed that many of the Kessel's troops were evacuated to the Frische Nehrung. Given the chaos characteristic of this stage of the war, however, it is unlikely that accurate figures will ever be determined. Many soldiers simply disappeared, and other elements of the 4^th Army continued to resist round Pillau, and then on the Frische Nehrung, until the end of the war in May.