The battle of stalingrad is believed by many to be one of the iconic events of the second world war. but how did the red army gain victory?

The red army gained victory by shutting out the supply routes to Stalingrad. No one came in or out. They trapped German soldiers inside so they could starve them out or force them to surrender. As winter rolled around, many of the Germans trapped inside the city died as a result of the severe cold weather as they were unprepared for the cold climate. Essentially, after they forced out the Germans, they reclaimed the city and held it down. Thus, a victory.