Unfortunately, in real life, there was no happy reunion for Vassili and Tania: by the battle's end, each thought the other dead, and Tania learned years later that not only was her lover still alive, but had recently married.
The duel between Zaitsev and Konig is partially based on records made by Zaitsev. The rifle scope taken from the killed German sniper is now at the Central Army Museum in Moscow, Russia. German who was shot in the duel was SS sniper Colonel Heinz Thorvald. The Germans claimed someone named Koenig had been shot in the duel and not Thorvald because they didn't want to admit their ace was down. This was claimed by Zaitsev, who also found the papers on the body identifying him as Thorvald.
It is estimated that the Germans suffered 260,000 soldiers killed in action with 90,000 captured during the battle of Stalingrad. The Russian casualties were much more severe with an estimated 500,000 soldiers killed and probably as many civilians.
"Enemy at the Gate" was the call for resistance in 1941 when the Nazis besieged Leningrad (now St. Petersburg, Russia). Leningrad resistance stopped the Nazis, and the words "Enemy at the Gate" became a call for anti-Nazi resistance everywhere. Same words are used in the book "Enemy at the Gate: The Battle for Stalingrad" (1973) by William Craig, which also documents the real-life war exploits of Vasilli Zaitsev.
Major Konig, played by Ed Harris,can be seen wearing gloves with the index finger and thumb on its right hand removed. This was quite common for snipers in cold conditions as it helped prevent frostbite in the hand, while allowing them to make delicate changes to their weapon and ensuring a smooth trigger squeeze.
In the large battle scenes it was deemed too dangerous with so many extras in a confined space to set off explosions by remote. Stuntmen were mixed in with the extras to set off the explosions by stepping on pressure plates.
At 54:10, one of the snipers burns his fingers on a field stove and quickly rubs them behind his ears. This is very realistic, as there is usually body oils accumulating there and it would ease blistering.
The trivia item below may give away important plot points.
Throughout the film, the only times Vasilli is ever seen killing anyone is at the beginning (in Stalingrad when he meets Danilov) and at the end (when he kills Konig) with the first being the only scene showing his sharp-shooting prowess.