Retired U.S. Navy Capt. John "Jack" Slaughter said people often ask him what the secret to his long life is.

"It was an awful lot of luck," he told friends and four generations of family — about 240 people from around the country and as far away as Canada — who gathered at the Colonnade in north Baltimore on Sunday to wish their patriarch a happy 100th birthday.

For one thing, Slaughter said, the first ship he served on was the only one in a group of four to survive a battle during World War II. The other three ships were sunk.

"I had no intention of being 100," he said in an interview earlier, after posing for photos with a family that includes his wife of nearly 75 years, Bess, 97, three children, nine grandchildren, 11 greatgrandchildren and a 92-year-old sister.

Wearing a suit and tie and grinning broadly, Slaughter stood through the whole photo shoot, resting his hands slightly on the back of Bess' wheelchair for support.

"I wouldn't have given you a plugged nickel to be here," he said. "But here I am."

The lobby of the Colonnade was taken over by tables, one of them filled with presents and cards addressed to "Captain Jack," as the assembled guests, handpicked by Slaughter, enjoyed a catered Sunday brunch. On another table were two birthday cakes, one with 100 candles.

"Nobody can draw a crowd like he can," said Slaughter's daughter, Anne Kern, of Oakenshawe.

The original budget for the birthday party was $6,000, "but he kept adding people," said his son, John Slaughter Jr., of Fredonia, N.Y. Ultimately, 240 of the 327 invited guests accepted.

Even his dentist in the Rotunda mall, George Shepley, came.

"He has all his teeth and his gums are healthier than yours," Shepley reported.

Also there was Carmen Tyson, of Rosedale, a nurse technician at Keswick Multi-Care Center in Hampden, where Slaughter recuperated after breaking his neck in a car accident in 2012. Tyson, who cared for Slaughter at the time, now gave him a hug and a kiss on the forehead.

"You don't want to kiss a 100-year-old man," said Slaughter, who earlier told a reporter there were more important things to write about.

Navy Rear Adm. Sean Buck, stationed in Washington, was on hand, too, although he is only related to Slaughter by marriage. His uncle, Lester Buck was married to Slaughter's sister, Margaret Ann Yeakley. Buck said he "absolutely" wanted to be there to honor Slaughter not only as a centenarian, but as a former naval officer and decorated war hero, whose accomplishments included commanding the USS Northampton, the presidential command ship for President John F. Kennedy.

Buck said his father and Slaughter also share a connection: both were born in Muskogee, Oklahoma, he said.

Standing on a stepladder to take group photos was Howie Soucek, of Franklin, Va., whose late father, Archie "Zeke" Soucek was a good friend and former Naval Academy roommate of Slaughter's.

Howie Soucek said the Slaughters represent what NBC News anchorman Tom Brokaw called "the greatest generation."

"They're such a great example for future generations," Soucek said.

Slaughter's children and grandchildren marveled not only at his longevity, but at his zest for life and new experiences.

Granddaughter Julia Gray, of Philadelphia, said she visits him about every six weeks and they discuss everything from the European interest rate to whatever computer problem he is having at the time.

"He's always learning," said daughter Mary Frank Slaughter, of Frankfort, Kentucky. "I don't think he's ever going to be old."

"I asked him if he felt any different today and he said, 'No different at all, great as always,'" said granddaughter Franny Legge, of Los Angeles, Calif., who grew up in Roland Park and graduated from Friends School. "I think what's kept him alive is his positivity — that and all the moderation he learned in the Navy."

Slaughter is the longtime president of his Naval Academy graduating class, with six of its original members still living, he said.

"I'm all for term limits," he quipped, "but I took this (presidency) on 20 years ago and I've never found anyone to take it over."

The last class reunion was in 2012.

"I don't know if there will be another," he said.

After lunch, everyone gathered at the cake table, where Slaughter, urging everyone to "eat, drink and be merry," quickly blew out all of the candles with the help of some of his greatgrandchildren.

As the smoke rose, Shepley, the dentist observed, "It looks like a naval battle."