William ‘‘Bud’’ Liebenow, the World War II naval lieutenant who guided his small vessel into Japanese territory to rescue John F. Kennedy and his crew after their boat PT-109 had sunk, died Friday in Mount Airy, N.C., where he lived. He was 97.

Mr. Liebenow died from complications from pneumonia, his daughter, Susan, of Arlington, Va., told the Associated Press.

A native of Fredericksburg, Va., Mr. Liebenow was a recent college graduate when the Japanese attacked Pearl Harbor in 1941. He joined the Navy and volunteered for service on the fast, small, and heavily armed attack PT boats.

Many of the US fleet’s larger vessels were destroyed or disabled at Pearl Harbor and the 80-foot PT boats became a mainstay of the early war effort in the South Pacific because the government could quickly mass-produce them. The boats, active almost exclusively at night, were used to harass and impede Japanese destroyers and cruisers without engaging them directly in battle.

Mr. Liebenow met Kennedy while both trained on the vessels in Narragansett Bay. Each eventually became captains of PT boats around the Solomon Islands.

The two were at the helm of their boats when a group of them encountered four Japanese destroyers at night on Aug. 1, 1943. After the PT boats separated, one of the destroyers rammed Kennedy’s PT-109, creating a massive fireball. Members of the closest PT boat assumed all the crew members had died.

Two sailors did perish. But Kennedy and 10 other crew members — two with severe injuries — were able to cling to the wreckage of the boat for much of the night before swimming to a small island more than three miles away.

After several days on their own, Kennedy encountered Solomon natives who were scouts for the Allies. He scratched a note into a coconut — “NATIVE KNOWS POS’IT . . . HE CAN PILOT . . . 11 ALIVE NEED SMALL BOAT . . . KENNEDY’’ — that Solomon Islands natives relayed to a US base.

Mr. Liebenow guided PT-157 behind enemy lines to rendezvous with Kennedy, who had left his crew to coordinate the rescue with an Australian officer.

Shortly after 11 p.m. on Aug. 7, 1943, after confirming each other’s identity, Kennedy and several natives rowed their canoe up to Mr. Liebenow’s vessel. Mr. Liebenow recalled the moment with The Boston Globe in 2002. He said he asked his fellow lieutenant comrade, then a ghost of a man wearing nothing more than tattered underwear, “So, what did you do with your boat?’’

“Gone,’’ Kennedy responded, then added, dryly. “Just one of those things.’’

Kennedy led Mr. Liebenow to the remote area where his crew was waiting.

“We had quite a celebration going back,’’ Mr. Liebenow said in a 2005 interview with the John F. Kennedy Presidential Library and Museum in Dorchester. “The pharmacist’s mate handed out all the medical brandy. And the natives knew one song in English . . . ‘Jesus Loves Me,’ and they were singing that.’’

Mr. Liebenow’s naval career didn’t end with that rescue. The following year, he commanded a PT boat that was part of the D-Day invasion of northern France. His PT-199 rescued men whose boats had been destroyed by Nazi defenders. Mr. Liebenow’s boat helped rescue about 60 crew members from the destroyer USS Corry, which was sunk during the invasion struggle.

‘‘We spent most of that day picking up guys out of the water,’’ Mr. Liebenow told the Mount Airy News in 2014.

He returned stateside after the war and worked as a chemist for the Chesapeake and Ohio Railway, his family said.

He told the Kennedy museum he was stunned in 1960 when he learned the man he helped save was running for president.

He credited Robert Kennedy, the campaign manager, with understanding the importance of the PT-109 sinking and incorporating it into the campaign.

In previous elections, John Kennedy had downplayed his role in the war.

Robert Kennedy asked for Mr. Liebenow’s help in campaigning in West Virginia and Michigan, where Mr. Liebenow had moved. The story of peril and survival resonated among voters.

At one point during a parade in Grand Rapids, the candidate turned to him and said, “Lieb, if I get the votes of everybody that claims to have been on your boat that night of the pick up, I’ll win this election easy.’’

The pressure from Kennedy’s political opponents could be fierce.

“They called up on the phone and used every trick to try to get me to say something that would be detrimental to Kennedy and his ability as a boat skipper. And I can’t say anything like that,’’ Mr. Liebenow told the museum.

In addition to his daughter, he leaves his wife, Lucy, and a son.

“Some people tried to blow the incident of the sinking. . . into making Jack Kennedy a great hero,’’ Mr. Liebenow said. “And other people tried to make it prove that he was a traitor. So you have the extremes.

“He never claimed to be a great hero. He was no different from any other PT officer.’’

Material from the Associated Press was used in this obituary.