Encirclement is a military term for the situation when a force or target is isolated and surrounded by enemy forces. The situation is highly dangerous for the encircled force. At the strategic level, it cannot receive supplies or reinforcements, and on the tactical level, the units in the force can be subject to an attack from several sides. Lastly, since the force cannot retreat, unless it is relieved or can break out, it must fight to the death or surrender.

A special kind of encirclement is the siege. In that case, the encircled forces are enveloped in a fortified position in which long-lasting supplies and strong defences are in place, allowing them to withstand attacks. Sieges have taken place in almost all eras of warfare.

Operation Winter Storm (German: Unternehmen Wintergewitter), a German offensive in December 1942 during World War II, involved the German 4th Panzer Army failing to break the Soviet encirclement of the German 6th Army during the Battle of Stalingrad.

In late November 1942 the Red Army had completed Operation Uranus, encircling some 300,000 Axis personnel in and around the city of Stalingrad. German forces within the Stalingrad pocket and directly outside were reorganized (22 November 1942) into Army Group Don and placed under the command of Field Marshal Erich von Manstein. The Red Army continued to allocate as many resources as possible to the planned Operation Saturn to isolate Army Group A from the rest of the German Army. To remedy the situation, the Luftwaffe attempted to supply German forces in Stalingrad through an air bridge. When the Luftwaffe failed and it became obvious that a breakout could succeed only if launched as early as possible, Manstein decided on a relief effort.

Originally, Manstein was promised four panzer divisions. Due to German reluctance to weaken certain sectors by redeploying German units, the task of opening a corridor to the encircled German 6th Army fell to the 4th Panzer Army. The German force was pitted against several Soviet armies tasked with the destruction of the encircled German forces and their offensive around the lower Chir River.

The German offensive caught the Red Army by surprise and made large gains on the first day. The spearhead forces enjoyed air support and defeated counterattacks by Soviet troops. By 13 December, Soviet resistance had slowed the German advance considerably. Although German forces took the area surrounding Verkhne-Kumskiy, the Red Army launched Operation Little Saturn on 16 December and crushed the Italian 8th Army on Army Group Don's left flank, threatening the survival of Manstein's force. As resistance and casualties increased, Manstein appealed to Hitler and to the commander of the German 6th Army, General Friedrich Paulus, to allow the 6th Army to break out of Stalingrad; both refused. The 4th Panzer Army continued its attempt to open a corridor to the 6th Army on 18–19 December, but was unable to do so without the aid of forces inside the Stalingrad pocket. Manstein called off the assault on 23 December and by Christmas Eve the 4th Panzer Army began to withdraw to its starting position. Due to the failure of the 6th Army to break out from the Soviet encirclement, the Red Army could continue the "strangulation" of German forces in Stalingrad.