It was the good war, the big war, maybe simply the war, and for the last week it has dominated television. Filmmaker Ken Burns is at it again, creating another visual icon, this one a tribute to the ordinary men and women whose extraordinary courage, determination and vision helped preserve our very ordinary lives.

But all of it – 15 hours over seven nights, some of it brutal, most of it uplifting – prompts a big question: Why does World War II, which started more than two-thirds of a century ago, cast such a shadow over our lives today?

The math of war

One answer comes from doing some elementary math. It is 68 years between the opening of World War II in Europe and the appearance of the Burns documentary. Now – to go back as far from World War II as we have just plunged back to reach the war – you must subtract 68 years from 1939. What do you get?

The answer is 1871, which is the year the Franco-Prussian war ended and also the year Germany was unified, the year the Third Republic was formed in Paris, the year Alsace-Lorraine was taken from France. All of those things contributed substantially to the mess that helped create World War II. We don’t live only in our own time; we also live in the past – or, perhaps more precisely, with the past.

But math isn’t everything, though you might be intrigued to know that adding 68 years to 1865, the year the Civil War ended, gives you 1933, the year Adolf Hitler came to power, and adding 68 years to 1933 gives you 2001, the year Osama bin Laden went global. (This suggests that 2069 is going to be a hell of a year. Someone please let me know how that turns out.)

No, it’s not so much math as chemistry and physics that matters. If you think of World War II as a series of chemical reactions, we have spent much of our lives watching those reactions play out.

“No one can contemplate the present state of things,” the British historian A.J.P. Taylor wrote in 1975, “without acknowledging that people everywhere are happier, freer and more prosperous than they would have been if Nazi Germany and Japan had won, and this applies as much to the countries under communist control as it does to the world of capitalist democracy.” That’s still true.

Ignorance of war

When we sit here in our comfort and our freedom (and our ignorance of the past), it is easy to think that war broke out in Europe, Pearl Harbor was attacked, America mobilized, and after three and a half years (less than the running time of the Iraq conflict) the war ended the way it should have and had to have.

Not so. There were many points in the war, particularly in the beginning, when victory was not assured at all, when the United States and its battered ally, Great Britain, seemed doomed, particularly in the Pacific.

Richard B. Stolley, who edited a Life magazine book on the war, spoke of “the astounding way the country rallied, from farm to factory to kitchen to battlefield, to help subdue a monstrous tyranny,” adding: “It was our finest hour, too.” I wasn’t there, but I think there was a breath of Rupert Brooke (wrong war, I know) to this struggle: “Now, God be thanked who has matched us with his hour.”

That’s why Mr. Burns and Lynn Novick, the co-producer and co-director of the series, were right to understand the central place World War II occupies in the life of those of us who live so far after that event.

Maybe it is because giants stirred on the Earth in those years. It was a period of great figures, so much so that Winston Churchill, recalling the summit at Tehran, could say: “There I sat with the great Russian bear on one side of me with paws outstretched, and, on the other side, the great American buffalo. Between the two sat the poor little English donkey, who was the only one who knew the right way home.” Need I explain that Churchill, Stalin and Roosevelt were in the same room, and need I comment that we don’t exactly have their replacements anywhere around here right now?

Greatest generation?

This is not to argue that the World War II folks were the greatest generation, a point of view that takes some explaining when you consider that another American generation produced George Washington, Samuel, John and Abigail Adams, Thomas Jefferson, James Monroe, James Madison, Benjamin Franklin, Alexander Hamilton, and the nameless thousands of Lexington, Concord, Valley Forge, Saratoga, Trenton and Yorktown. It is merely to say that great events, with great consequences, were played out in the lives of people who are still alive, many of whom we meet every day in the store and on the corner.

“This was, in fact, a struggle not only for control of territory and resources, but about who would live and control the resources of the globe and which peoples would vanish entirely because they were believed inferior or undesirable by the victors,” Gerhard L. Weinberg of the University of North Carolina wrote in his massive global history of the war.

Some reviewers have called the PBS series exhaustive but also exhausting. Tough luck. More exhausting than the Bataan death march, which was portrayed in the first hour of the telecast? More exhausting than D-Day? Spare me, please.

“It’s a monumentally important event in the history of the 20th century, and its reverberations will echo for many years and though many generations,” Ms. Novick said in an interview. “It was a transition point for the United States from a backward nation to an international player and the greatest industrial power in the world. It unleashed a whole array of social changes. It was the biggest war ever, with the most gargantuan effects. It was a formative moment for our people, and we’ll never know enough about it.”

Thanks to her and Mr. Burns, we now know more, and we know why we need to.