Investment is the military process of surrounding an enemy fort with armed forces to prevent entry or escape. It serves both to cut communications with the outside world and to prevent supplies and reinforcements from being introduced.

The Battle of Stalingrad occurred on the Eastern Front of World War II, beginning when Nazi Germany and its Axis allies attacked and became locked in a protracted struggle with the Soviet Union for control over the Soviet city of Stalingrad in what is now southern Russia. The battle was characterized by fierce close-quarters combat and direct assaults on civilians in aerial raids; the battle epitomized urban warfare and is recorded as the single largest and costliest urban battle in military history. It was the bloodiest and fiercest battle of the entirety of World War II—and arguably in all of human history—as both sides suffered tremendous casualties amidst ferocious fighting in and around the city. Today, the Battle of Stalingrad is commonly regarded as the turning point in the European theatre of World War II, as Germany's Oberkommando der Wehrmacht was forced to withdraw a considerable amount of military forces from other regions to replace losses on the Eastern Front. By the time the hostilities ended, the German 6th Army and 4th Panzer Army had been destroyed and Army Group B was routed. The Soviets' victory at Stalingrad shifted the Eastern Front's balance of power in their favour, while also boosting the morale of the Red Army.