In Moscow's Red Square, Russian soldiers in historical uniforms and armored vehicles take part in a rehearsal for a parade marking the 77th anniversary of the 1941 Battle of Moscow. (Yuri Kochetkov/EPA-EFE/REX )

Today is the anniversary of the opening of the 1941 Soviet offensive at the Battle of Moscow: the first major defeat suffered by Nazi Germany and perhaps the most important turning point of World War II in Europe. It is a day to remember the immense losses that Russians and other peoples under Soviet rule suffered in the war, and to acknowledge their central role in Allied victory.

Without Soviet manpower and blood, the outcome might have been very different.

In the two years preceding the Battle of Moscow, German troops had won sweeping victories in Poland, Norway, France and the Balkans, giving Adolf Hitler mastery over Europe. Joseph Stalin, fearing Germany and hoping to avoid war, signed a nonaggression pact with the Nazi leader in 1939 and helped him crush Poland.

But Hitler’s ultimate target was the U.S.S.R., which he saw as the center of the “Jewish-Bolshevik conspiracy” he imagined was plotting to rule the world. On June 22, 1941, Germany launched its attack on the Soviet Union.

In the first five months of the invasion, German forces inflicted one catastrophic defeat after another on the Red Army. The Soviet military was powerful on paper, but much of its equipment was obsolete, its training often poor and its inventory critically short of the tools that made precision targeting possible — radios, optics and even maps of its own territory.

By early December, total Soviet losses were approaching 3 million, and both U.S. and British intelligence feared that the Soviet Union could collapse within weeks.

As the Soviets retreated, the German military and occupation authorities inflicted even greater suffering on the population than Stalin’s murderous regime had. Regular troops and SS death squads executed hundreds of thousands of Jews and real or suspected Communists. The collective farms, the cruel Soviet instrument for exploiting the peasants, were kept in place. Mass rapes, random murders, the torching of thousands of towns and villages — this was one of the most brutal occupation regimes in history.

Why? Because it fit the Nazis’ long-term goals: extermination of the Jews, slavery and ultimate extinction for the Slavs.

In early December, German units were within 20 miles of Moscow. Then the weather changed. Temperatures around 10 degrees Fahrenheit, waist-deep snow and poor visibility prevented the Germans from using their blitzkrieg tactics. Combat would be at shorter ranges, and heavy equipment — vehicles, tanks, aircraft, artillery — would be much harder to operate.

This was the moment that Soviet Gen. Georgi Zhukov chose to strike back. At 3 a.m. on the morning of Dec. 5, 1941, five hours before dawn, Soviet troops attacked across the frozen Volga River.

In the ensuing fighting, both sides endured extraordinary cold and hunger. But the Soviets were better equipped for winter fighting, and now they could get in close. Tramping through blizzards, they surrounded the villages outside Moscow where the German soldiers hunkered down and engaged their enemy at close quarters, in confused firefights and even at bayonet point.

In one month of desperate struggle, the Germans were thrown back over 100 miles from Moscow. The Soviet capital was saved.

The battle tested the absolute limits of human endurance. Soldiers on both sides were often subsisting on the flesh of dead draft horses and a few frozen potatoes found in windswept fields. In a letter written to his family, confiscated by the secret police as “defeatist,” one Red Army man wrote, “We are struggling through villages and forests … [our officers] drive us like cattle … winter has hit us, cold and hunger and typhus.”

Both sides were executing prisoners of war, so the troops tended to fight to the end rather than surrender. Some were driven out of their minds by rage, exhaustion and the thirst for vengeance. On Dec. 16, a German soldier who escaped from Soviet captivity reported to his unit intelligence officer that a drunk group of Red Army men, seemingly lost in the snow with no commander, had murdered his fellow POWs, butchered them and eaten their livers and lungs.

The Battle of Moscow was closely linked to events half a world away. The Soviet Union had long had a hostile relationship with imperial Japan, and Stalin feared a Japanese attack on Siberia would follow the Nazi assault. But in October 1941 he learned from a Soviet spy that the Japanese leadership had decided against an attack on the Soviet Union. This information enabled Stalin to transfer some of the Red Army’s crack units in Siberia to the Moscow region, where they were key to Soviet victory in December.

Unknown to Stalin, the Japanese had shifted their focus to an attack on U.S. and British possessions in the Pacific. On Dec. 7, 1941, just 60 hours after the Soviet counteroffensive at Moscow began, Japanese aircraft attacked U.S. military installations around Pearl Harbor, Hawaii.

The Soviet victory at Moscow meant that the U.S.S.R. would continue to fight at least into the summer of 1942, condemning Nazi Germany to a long war of attrition. The attack on Pearl Harbor meant that the United States, with all of its industrial might, would enter the war. Taken together, Moscow and Pearl Harbor meant that Axis forces were almost certainly doomed to defeat.

The Battle of Moscow also reminds us of a truth that many Americans do not know: It was the Soviet Union that made by far the biggest contribution to the defeat of Nazi Germany.

All honor to the 400,000 Americans who died in the war, and to the millions of others who fought and died for the Allied cause, from Britain, France, Poland, Serbia, India, China and many other lands. However, the Soviet Union suffered more losses than any other combatant power: 11 million military dead and another 16 million civilian. And between 1941 and 1945, it was the Soviets who fought most of the German military and inflicted most of the German casualties.

One can say this without apologizing for communism or Stalin’s mass murder. Indeed, my research suggests that Soviet troops fought more in the defense of their homeland and their families than they did for Stalin. At the very least, the Soviet sacrifices saved the lives of hundreds of thousands, if not millions, of young men from the United States, Britain, Canada and many other nations who would have died in an assault on the sea approaches of “Fortress Europe” manned by the entire German military.

The high cost of the war affected Soviet strategic thinking for decades and still influences Russian international policy today. The U.S.S.R. held onto its empire in Eastern Europe for 40 years in part to have a buffer zone against possible attack from the West. Russian worries today about possible expansion of NATO to Ukraine have similar roots, even though Putin’s aggression in the region is clearly unjustified.

It is essential for Americans to acknowledge and respect these realities. Russians are acutely aware that the magnitude of their sacrifice is not understood in the United States. Indeed Vladimir Putin’s regime has won popular support in part by exploiting Russians’ sense that their country is not respected in the world and their history is not understood. Paying tribute to the overwhelming contribution of Soviet men and women to victory in World War II and commemorating their losses would go a long way to soothing that sense of grievance and improving Russian-American relations.