In the spring of 1942, Larry Kirby walked out of St. Mary’s High School in Brookline right into the Marines. He was 5 feet 6 inches tall and 135 pounds soaking wet.

When he got to Parris Island, S.C., the drill instructors nodded approvingly as he hit everything he aimed at on the range. He was wiry and could move like a cat, so they sent him to recon scout training.

But when he arrived at Iwo Jima on Feb. 23, 1945, there was no scouting to be done. Just fighting. By that time, Kirby was a 20-year-old platoon sergeant, responsible for the well-being of 45 Marines.

The Americans wanted the island for the airfields. They figured there might be 10,000 Japanese defenders on Iwo Jima. Turned out there were twice that many, hidden in a maze of tunnels.

Kirby and the men of Easy Company of the Second Battalion of the Ninth Marines, Third Division, had fought their way through the jungles of the South Pacific only to land on the barren moonscape of Iwo Jima. The only color was the thick red blood on the sandstone.

”We’d fight our way up toward the Japanese bunkers, moving one guy at a time, get close enough to throw in a grenade or hit them with a flamethrower. They used the tunnels to reinsert men and fire at us from behind. Some days, we moved just 10 or 15 yards."

On that first day, Larry Kirby was lying flat when he heard a Marine nearby yell, "Look!"

Kirby rolled on his back and looked back toward Mount Suribachi, which, despite its grandiose name, was no more than a hill. He saw five Marines and a Navy corpsman push up an American flag. From a little more than a football field away, he watched as one of the most indelible, iconic images of all time unfolded in front of his eyes.

”When that flag went up, all that meant to me is the hill was secured. We wouldn’t be taking any more fire from there. It was a huge morale boost."

It took the Marines five weeks to secure Iwo Jima. By then, there were 20,000 Japanese and 7,000 Americans dead. Kirby’s battle ended after 22 days when Easy Company was relieved. Of the 230 Marines of Easy Company who landed, only Kirby and six others were left standing.

On Monday, 70 years to the day he found hell on earth on Iwo Jima, Larry Kirby sat in his house on the North Shore, marveling at the arbitrary nature of life.

”I didn’t do anything special," he says. "I just showed up and did my job and got lucky."

He thinks his physique had as much to do with it as anything. Bigger Marines right next to him took shrapnel and bullets that missed him.

”It was like trying to shoot a pencil," he says.

Last week, he got together with other Massachusetts veterans who survived Iwo Jima, great Americans like Al Richards, Harry Wildasin, Sammy Bernstein, Bob Johnston, Richard Gates, Bob Lavoie, and Jim Delaney.

It was good to see them, and it’s great that the younger Marines who make the gathering happen every February don’t forget them. But Larry Kirby never joined a veterans group. He never went back to Iwo Jima because he never wanted to.

Instead, he remembers in his own way.

”When I sit, alone, I remember all the guys who died. I can still see their faces. I can still hear their laugh."

There was a young Marine in his platoon, Hal Karbin. He had a chipped tooth. Larry Kirby still sees Hal Karbin’s chipped smile.

”It seems so unfair. I have lived 90 years. Married to my Mary for 68 years. Four kids, eight grandkids, four great-grandchildren. And these guys died at 18, 19. They never went to college. They never had families. That’s not fair."

Larry Kirby knows better than most that if life is sometimes unfair, war always is.