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.
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 oil accumulating there and it would ease blistering, and touching the earlobes after burning your fingers will help transfer some of the heat away thereby easing the pain.
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.
Apart from Ron Perlman's "English Accent"...all characters use their normal speaking voices without modifying or mangling them for their characters' country of origin. For example, Ed Harris plays an Aristocratic German/Prussian Officer but he speaks in a normal American accent as he is an American actor. There isn't the "Germanized" English that you see in so many war movies.
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.
The film depicts Zaitsev as a bit of an unschooled simpleton, from some backwater part of the country, but who knew how to shoot a rifle. In reality, Zaitsev was an educated man, and had worked for five years as an accountant in the Russian navy stationed in the Pacific before joining the army.
In the film Zaitsev and his comrades seem to be exploited by the communist leadership, seemingly being thrown into the horrors of war ignorant of what they were facing, viewed mostly as nothing more than cannon fodder. According to Zaitsev's own writings on the war, however, he and his comrades in the navy for a long time begged their superiors to transfer them to the army so that they could fight at Stalingrad, knowing full well what they were volunteering for.
The wreckage of a German aircraft outside the department store scene is a Siebel Si204, a light military transport built in small numbers. It is consistent with the period and the markings are authentic for the Russian Front. It was built in France and Czechoslovakia, as well as Germany, and many were operated by both civilian and military air fleets until the 1970s. It is clearly a mock up, however, and the tailplane is wrong: it is a single tailplane and the 204 had a twin tail.
Having served for years in the Russian navy before being transferred to the army, Zaitsev was proud of his naval background and wore his blue and white striped navy issued shirt under his uniform during his time in Stalingrad.
The locomotive used for filming the troop train scene is, ironically, a German-built "Kriegslok" ("war locomotive"). About 2700 were captured by the Soviets but not used by the Soviet Railways until after the war (see Goofs).
The trivia items below may give away important plot points.
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. Or at least, so she claimed. According to Vassili, they were never lovers, and in fact, he was never in any relationships during the war.
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.