Stalingrad

In August 1942, German soldiers enjoy leave in Cervo, Liguria, Italy after fighting in North Africa. An assembly is then held and several of the men are awarded, including Unteroffizier Manfred "Rollo" Rohleder (Jochen Nickel) and Obergefreiter Fritz Reiser (Dominique Horwitz), who are both introduced to Leutnant Hans von Witzland (Thomas Kretschmann), their new platoon commander. The unit is promptly sent to the Eastern Front to participate in the Battle of Stalingrad.
Witzland's platoon joins a company commanded by Hauptmann Hermann Musk (Karel HeÅmÃ¡nek). Musk leads an assault on a factory, which results in heavy casualties and the survivors being surrounded in a decrepit building. After a botched ceasefire to rescue some wounded outside, they capture Kolya, a young Russian boy. The Russians attack again the next day, and Kolya escapes in the confusion. With the radio not working, von Witzland, Reiser, Rollo, Emigholtz (Heinz Emigholz), "GeGe" MÃ¼ller (Sebastian Rudolph) and WÃ¶lk (Zdenek Vencl) enter the sewers to go for help. Witzland gets separated from the others and captures a Russian soldier named Irina (Dana VÃ¡vrovÃ¡), who offers to lead him to safety in exchange for her freedom, but when he is not looking she pushes him into the water and escapes. His men rescue him, and Emigholtz is found severely wounded by an explosive trap; they take him to a crowded aid station, where Reiser forces an orderly at gunpoint to work on him. Emigholtz dies anyway, and they are arrested by Hauptmann Haller (Dieter Okras), who has already clashed with von Witzland. They end up in a penal battalion disarming land mines.
Four weeks later, a brutal winter has set in and the Soviets have utterly surrounded the German Sixth Army. Hauptmann Musk thus reassigns the penal battalion â which includes disgraced fellow officer Otto (Sylvester Groth) â to combat duty. Witzland's platoon defends a position from a Russian tank column, and emerge victorious after a bloody battle (during which WÃ¶lk is killed). Hauptman Haller later orders von Witzland and his men to execute some unarmed civilians, including Kolya, whom Witzland tries to save but to no avail.
The horror of the siege finally takes its toll on the men; Witzland, GeGe, and Reiser thus decide to desert and head towards Pitomnik airfield in hopes of catching a plane back to Germany, stealing medical tags from some dead bodies along the way to feint being injured. By the time they arrive, the last transport takes off without them as the base is shelled by Russian artillery. They rejoin the others in the shelter, where they find Musk suffering from severe trench foot. A German aircraft suddenly drops a container full of supplies, and the men rush out to devour its contents. Haller appears and holds them at gunpoint, but is subdued by von Witzland and shot by Rollo; Haller accidentally shoots GeGe as he falls, killing him. He then pleads for his life, telling them about the supplies he is hoarding in a nearby house before being executed by Otto.
In the house's cellar they find shelves stocked full of food and liquor, and Irina tied to a bed. Von Witzland cuts Irina free and befriends her, sharing in her despair over the dire situation. As the rest of the men gorge themselves, a deluded and dying Musk tries to rally them to rejoin the fighting. Otto becomes hysterical and commits suicide. Rollo, the only one to obey the order, is last seen carrying Musk's corpse outside, only to find the Sixth Army surrendering to the Russians.
Irina offers to help Witzland and Reiser avoid capture, but while trudging through the snow they are shot at by the Soviets; Irina is killed and Witzland is mortally wounded. The Germans get away, but Witzland eventually becomes too weak and dies in Reiser's arms. Reiser cradles his body, reflecting on his time spent in North Africa before freezing to death.

Question: Who have surrounded the German Sixth Army?
Answer: The Soviets