At least four Pearl Harbor veterans, three in their late 90s and one who was 100, recently died within weeks of one another as the clock rapidly ticks down on the last survivors from the day that changed America on Dec. 7, 1941.

Will Lehner was a Navy reservist on the USS Ward, which spotted, fired on and sank a Japanese midget submarine trying to sneak into Pearl Harbor more than an hour before the aerial attack began.

It would take another 61 years and a submersible’s visual sighting of the sunken sub — with Lehner himself making a subsequent reconnaissance dive — to prove that the Ward had put a round from one of its 4-inch guns dead center through the base of the Japanese submarine’s conning tower.

Lehner, 98, died Jan. 5 in Wisconsin.

Delton “Wally” Walling was a 19-year signalman second class who watched in horror from the harbor control tower as Japanese planes flew 30 feet below him and 100 feet off to the side dropping torpedoes that slammed into the ships of Battleship Row.

“You would look right in their plane and see the pilot, his scarf flying out through the canopy, but he’s looking directly ahead because he has such a short area to get down over those buildings and get down to the water to drop those torpedoes,” Walling recalled in 2014.

Walling wasn’t supposed to be in the harbor tower that day.

“I had a buddy who owed me $400, and he was being transferred in a couple of days and I knew I’d never see him again,” he said. “So I was up there trying to get what I could.”

The California man died Jan. 8 at age 98.

“It’s the passage of time. It’s hard to believe they’ve had these full lives and lived this long. It’s very hard for us to let them go — as if they are immortal,” said Daniel Martinez, chief historian for the Pearl Harbor National Memorial.

Joe Walsh, who made it to 100, was a Marine in the Pearl Harbor Navy Yard who manned an anti-aircraft gun and shot back at the attacking Japanese planes, according to the Los Angeles Times.

“I didn’t have time to get scared,” the newspaper quoted Walsh saying. “You didn’t think about it. You did what you were told to do.”

Walsh, co-founder of the North San Diego County chapter of the Pearl Harbor Survivors Association, died Dec. 21 at the Pacifica Senior Living Complex in Vista, Calif., the Times said.

Marion Harris was 97 when he died Dec. 26 in Virginia. Harris was assigned to the USS Vega, a cargo ship, that arrived in Hawaii on Dec. 6, 1941, and was at Pier 31 in Honolulu Harbor at the time of the attack, according to Pacific Historic Parks, a nonprofit that helps support the USS Arizona Memorial.

The crew opened fire with the ship’s anti-aircraft guns as civilian stevedores unloaded cargo.

“Although the USS Vega was not moored at Pearl Harbor, she was an active naval vessel on Oahu on Dec. 7, 1941 (and) therefore, her crew are all Pearl Harbor survivors,” Pacific Historic Parks said.

Lehner, the USS Ward veteran, was a member of the crew that radioed in the claim that it had fired on and dropped depth charges on a submarine operating in the defensive sea area at 6:45 a.m. Dec. 7, 1941.

Notified of the report, Adm. Husband E. Kimmel, head of the U.S. Pacific Fleet, was skeptical.

The two-man sub was one of five attached to Japanese I-class mother submarines and launched in connection with the aerial attack. All would be unsuccessful in their mission.

In 2002 two deep-diving submersibles operated by the University of Hawaii’s Undersea Research Laboratory found the 78-foot midget sub during test and training dives.

The vessel was upright in 1,300 feet of water 5 miles south of the mouth of Pearl Harbor, two torpedoes still in place. A hole punched through the conning tower from one of the Ward’s 4-inch guns was clearly visible. The projectile had apparently not exploded.

Lehner saw the damage firsthand in 2002 on a submersible dive to the wreck site.

“I knew we had sunk it, but when someone said, ‘You’ve got no proof,’ I had to be quiet because I had no proof,” Lehner recalled in 2005.

With the discovery, the Ward’s actions were no longer in doubt: It, not the Japanese, had sunk the first vessel in the attack on Pearl Harbor.

The National Park Serv­ice’s Martinez said he was able to be in the submersible with Lehner to see the midget submarine, which “was incredible.”

Some Pearl Harbor veterans did oral histories and wrote books.

“But for the visitor, that kind of gleam they get in their eye when they went out to shake (a Pearl Harbor survivor’s) hand and have a picture taken with them or get a book signed — that is what I think everyone is going to miss,” Martinez said. “It’s going to be part of the Pearl Harbor experience that has slowly faded away.”