Seventy years ago this week, on Sept. 1, 1939, the Second World War broke out with the German invasion of Poland. Thousands of books have been written about the war. And by now revisionist historians of revisionist historians engage in an endless cycle of disagreement over why the war started, how it ended and what it all meant.

Here are a few more controversial thoughts on the horrific conflict that killed 60 million people, wrecked Europe and set the stage for an ensuing half-century Cold War.

Many blame Germany's aggressions on the supposedly harsh terms of the Versailles Treaty following the First World War, which stripped a defeated Germany of territory, required reparations and dismantled its military.

But Versailles was far more lenient than what the Germans had planned for Britain and France should they have won in 1918. And it was not nearly as harsh as the terms the Germans imposed on a defeated Russia under the Treaty of Brest-Litovsk in early 1918, before they lost the larger conflict.

A better reason there was a Second World War, but not a Third, is that Germany was occupied and monitored after 1945 — unlike following its previous defeat in 1918.

Most give the Red Army the most credit for wrecking the German army. That is true: Two of three German soldiers who died in the war were killed on the murderous Eastern Front, a larger theater of conflict than all others combined.

Yet despite the superhuman heroism of millions of brave Russian soldiers, Stalin's Soviet government was largely an amoral actor throughout the war. It, along with Hitler's Germany, invaded neutral Poland in September 1939. Three months later, it attacked Finland.

Until the day it was invaded by Hitler, Stalin's Soviet Union had provided Nazi industry with much of its strategic materials used to defeat and occupy democratic Western Europe. Communist Russia renounced most of its wartime promises, guaranteeing that a war that started to free Eastern Europe from totalitarian government ended by ensuring it under Soviet control.

Lately, the role of the United States in World War II has been downplayed, since we came late to it, and suffered the fewest military and civilian casualties of the major Allies. But no other power fought on so many fronts in so many crucial ways: strategic air campaigns against Germany and Japan; invasions of North Africa, Sicily, Italy, Western Europe and the Pacific islands; submarine and surface fleet operations against Germany and Japan; and convoys and supplies to Britain, China and the Soviet Union.

It has become fashionable to diminish the British role, given that by 1943 its manpower reserves were exhausted and the bulk of the later fighting against the Axis was conducted by Russian and American troops.

In fact, Britain nearly alone saved Western civilization between September 1939 and June 1941. From May 1940, it fought almost alone against the entire continent of occupied Europe, when the U.S. was still isolationist and the Soviet Union was actively helping the Nazi cause.

We also forget that the Allied victory was not foreordained. By December 1941, the odds were all in favor of the Axis powers. They had been arming since the mid-1930s. Hitler controlled much of the present-day area of the European Union and its surrounding environs from the Atlantic Ocean to the suburbs of Moscow, and from the Arctic Circle to the Sahara Desert. Much of China and almost all of Southeast Asia were under Japanese control.

Why did the Allies recover and win? Largely because of Russian manpower, the American industrial colossus and British wartime experience. By 1944, the Allies had the best and most numerous tanks, artillery and planes; the largest armies; the best wartime leadership in Churchill, Roosevelt and Stalin; and the most adept generals.

Did any good come from such a monstrous bloodletting?

Perhaps. The Holocaust was finally stopped before every Jew in Europe was killed as Hitler had planned. Germany, Italy and Japan were transformed from monstrous regimes into liberal states whose democracies have done much for humanity in the ensuing years. And Western civilization survived its own heretical cannibals — to foster in the ensuing decades the greatest growth in freedom and prosperity in the history of the planet.

Victor Davis Hanson is a classicist and historian at the Hoover Institution at Stanford University. Reach him at author@victorhanson.com.