This summer will mark the 75th anniversary of D-Day, the day thousands of men landed on the fog-covered beaches of Normandy to attack Nazi Germany’s army. What were these men fighting for? What was at stake for those fighting the deadly World War II? Scholar and professor Victor Davis Hanson answers these questions in a new free online course from Hillsdale College, “The Second World Wars.”

Sixty million people died in WWII: half soldiers, airmen, and sailors, the other half civilians. That’s three times as many casualties as in World War I. Technology and wealth made WWII a new kind of war: one that introduced not just new ways of killing people, but new ways to increase the volume of people killed.

Years before the war even started, both Germany and the Soviet Union were engaged in mass-produced efforts to kill their own people. The Soviet Union’s Joseph Stalin was starving his people to death, and Germany’s Adolph Hitler was creating factories to make killing people more efficient. Gassing Jews in trucks and shooting them both took too long, and upset the soldiers, so the Nazis took a more scientific approach to their genocide.

While it’s hard to comprehend what means could justify these horrific ends, it’s important to look at the motives of such tyrants. They did not kill because they simply loved cruelty, but because they sought perfection. They desired to eliminate what they saw as problems in society — the obvious example that Hitler’s answer to eliminating class oppression was to eliminate an entire class of people.

Ultimately what the Axis and Allies were fighting over was the meaning of human nature. Is the human soul free and entitled to self-government, or are humans collective beings shaped by history? If it’s the latter, then the person appointed to the top has all the power to shape history.

The Axis argued that humans are shaped by their race and class, so controlling those variants meant the ability to create their vision of a perfect society. This is this impetus of tyranny. In tyranny, the rules of the land are held in the interest of the ruler. This is what Winston Churchill was determined to fight against, as he declared in his statement in the House of Commons on May 13, 1940:

You ask, what is our policy? I will say: It is to wage war, by sea, land and air, with all our might and with all the strength that God can give us; to wage war against a monstrous tyranny, never surpassed in the dark and lamentable catalogue of human crime. That is our policy. You ask, what is our aim? I can answer in one word: victory; victory at all costs, victory in spite of all terror, victory, however long and hard the road may be; for without victory, there is no survival. Let that be realized; no survival for the British Empire, no survival for all that the British Empire has stood for, no survival for the urge and impulse of the ages, that mankind will move forward towards its goal.

Germany and Japan were fighting for total control of the world around them, via control of the people under them. The United States and the British Empire were fighting for human freedom, a product of human nature. Just as Churchill argued, if the allies had failed to defeat the spread of totalitarianism and communism, they would have failed to secure a flourishing future for all of mankind.