Stalingrad 

On July 17, 1942 the German troops reached Stalingrad, a town of 400,000 people on the Volga River, and the bloodiest battle in human history had begun. Photo: this is how Stalingrad looked a few days before the battle (July, 1942):

And this is how it looked when it was over, 6 months later (February, 1943):

 

Hundreds of thousands soldiers clashed in the ruins for several months. The fights were fierce: an average life expectancy of a soldier in Stalingrad was 1 day. During the defense of Stalingrad, 1 Russian soldier died every 25 seconds. On November 19, 1942 the Russians launched an unexpected counter-offensive  - Operation “Uranus”, and in 4 days surrounded the city,  blocking 265,000 German soldiers inside. Attempts to break the blockade failed, and the Germans started suffering from exhaustion, starvation and cold.

Finally, on January 31, 1943 Ernst Paulus, the commander of the German army in Stalingrad, capitulated - against Hitler's orders. A 3-day National Mourning was announced in Germany, and came as a shock to the German public, who believed that the war was almost over. Photo: Field Marshal Paulus and his chief of staff after their surrender:

The Battle of Stalingrad was the bloodiest battle ever, with 2,000,000 casualties. For the first time since the invasion, German losses were almost as high as the Russians'.  25% of the entire German military strength on the Eastern front was destroyed. The Battle of Stalingrad marked the point were the Germans lost the strategic initiative for the rest of the war, and in Russia it is considered the turning point of WW2.