... on the day The Stalingrad Battle ended on February 2, 1943. By then, Soviet people knew that they will win the war.
More than 2 million casualties, more than a million KIAs, a complete destruction of Wehrmacht's 6th and elements of 4th Armies, annihilation of Italian, Hungarian and Romanian armies. Compare this with victory over 50,000 Germans at Alamein. Just numbers and scales.