REPORTER’S NOTEBOOK:

When the bombs started falling Dec. 7, 1941, all the scrawny little guy from Iowa knew was that instead of being at breakfast he was suddenly at war. A Marine radar operator for all of six months who had never left his home state before that year, he wouldn’t be your first pick for a hero.

But like everyone around him, Bob Wilkinson pulled out his bolt-action Springfield rifle, climbed onto the roof and started shooting into the sky. He was my grandfather, and he had more guts in that moment than anyone I can imagine.

No, he didn’t take down one of the Japanese planes out to cripple the Pacific Fleet. Neither did anyone standing next to him. But he had to do something against the disaster.

Later, things got grimmer as he went down to the docks to help with the carnage, where he told my uncle he saw “bodies stacked up like cordwood.”

I’m writing this because time is tough on national memory, and the country has moved on from a 66-year-old act of war. News outlets reported last year that the national Pearl Harbor Survivors Assn. was having its very last national meeting. Why? Like the man I remember as Grandpa Bob, most who survived that day are no longer with us. When he died more than 10 years ago, other survivors came to his wake dressed in their Hawaiian shirt uniforms to pay their respects, but one day none will be left to do so.

In a very real way, the firsthand memories of a defining national moment are disappearing. It will happen one day to the Kennedy assassination, the moon landing, and one day, even 9/11 — a day that drew its own comparisons to Pearl Harbor, but highlighted just how long ago it really was. But something like that Sunday-morning air raid, whose survivors were always a special few to begin with, shows us how all too quickly a memory fades into the history books.

That’s why it’s important to pass on the stories we have. Every time we do so, we show how the past was something full of living people, and that these decisive moments changed real lives.

Bob mined stories out of his war years in the South Pacific for the rest of his life. The tales he told my mother and uncle about the war were usually the lighthearted ones, like his injuries sustained defending the only case of beer his bunkmates had from some jealous soldiers who faked an emergency drill to steal it. But he also proudly showed off his survivor’s license plate, and when he went back to Hawaii years later, my uncle says he came back visibly moved.

The raid was far from the last time he put his life on the line. Practically as soon as it was over, he was packed onto a ship with the only working radar gear in Hawaii and headed to the fierce combat of the Battle of Guadalcanal. You could say he had unbelievable luck to make it through all of that with nothing more than a broken tooth. But it was the raid that changed everything, and turned this cornfed 5-foot-7 Iowa teenager into a man, and a hero.

My mother and uncle, his daughter and son, never forgot that. Mom proudly took his medal to the film “Pearl Harbor” when it came out a few years ago, but she came out furious the movie didn’t have a single Marine in it. She still raises her American flag every Dec. 7, but she’s the only one on her block who does. And for the Iraq-bound Marine in her Spanish class this year, she plans to take out the medal one more time and tell a story or two.

So on Friday, I’ll do my part. I’ll think of my grandfather, up on that roof, aiming upward, doing the one thing he knew how.

MICHAEL ALEXANDER can be reached at (714) 966-4618 or michael.alexander@latimes.com.