The letters written during World War II by Bobby Vath, a young sailor from New Orleans, and Jeanne Daste, his girl back home, were delivered twice. But only the first delivery was through the U.S. Postal Service.

The second came courtesy of Hurricane Katrina.

Between Vath and Daste’s marriage in 1946 and the floods after Katrina in 2005, the nearly 700 letters apparently rested in a Navy sea bag that accompanied the couple on moves to several homes.

One of their six children, Emily Nolan, remembers being aware of the canvas bag, kept on a closet shelf and declared off-limits to her and her siblings when they were growing up.

“We were told it held correspondence between my parents during my dad’s Navy tour. My mother was very protective of this mysterious bag, and we were never, ever allowed to touch it,” Nolan said.

In 1979, the Vaths moved to a home on West End Boulevard, where he died in 1998. She died two years after that, but the house stayed in the family.

It was heavily flooded in Katrina’s wake. And after the flood waters subsided, the sea bag — unseen for decades — was found at the foot of the basement stairs.

“It had never been there before,” said Emily’s husband, Bruce Nolan.

Indeed, no one even knew that the bag had made the move from the Vaths’ previous home.

Still more incredible: Despite being wet, some stuck together and all fragile, the letters remained readable.

In 2009, when Emily Nolan retired as an oncology nurse, she adopted their transcription as her project. This led to self-publication of selected letters as a private family memoir, “The Sea Bag: Hurricane Katrina and a Love Revealed.”

Emily and Bruce Nolan, who worked on the memoir together, spoke at a recent Lunchbox Lecture at the National World War II Museum, recounting their experience for others interested in preserving family correspondence or self-publishing a family history.

The museum has its own interest in wartime memories. One of its missions, stated on its website (nationalww2museum.org), is “to preserve the legacy and lessons of World War II through the stories of those who experienced the war.” To this end, it accepts donations of oral histories and memoirs that people have conducted or printed themselves.

Emily Nolan told the packed auditorium that some letters took just an hour to transcribe, but others took days.

“I developed a set of techniques to decode faint letters,” she said. “Sometimes I’d go to a window and rock a letter back and forth in the light to raise the faintest impression left long ago by a pen.”

By mid-2013, she had finished the transcription and her husband had retired as a reporter for The Times-Picayune. In early 2014, the Vath family asked the Nolans to turn the letters into a book.

This called for a prologue, introducing Vath and Daste, and an epilogue summarizing the couple’s post-war life together.

Then came the chore of editing nearly 400,000 words down to a readable total.

“We tried to keep conversational themes intact,” Bruce Nolan said. “As each writer asked questions, we tried to include the letters that provided the other’s answers.”

Next step: turning the manuscript into a book.

One method is to use a turnkey self-publishing operation, a number of which can be found through the Internet.

“For a set fee, usually about $3,000, they will assign your manuscript to a freelance editor to work with you. They will design the interior of the book, design front and back covers, print as many copies as you like for an additional fee and assist with basic marketing,” Bruce Nolan said.

Another option is to subcontract the book yourself, which is what the Nolans did. They hired a local graphic designer, David Johnson, for the design work and had the book printed by Family Heritage Publishers in Salt Lake City.

“There are small printing houses around the country who will turn out nice hardback volumes without requiring minimum press runs of 1,500 or 5,000 copies,” Bruce Nolan said.

“We printed 116 copies. Our whole cost, from beginning to end, was about $4,200.”

The book is intended for family members. Bruce Nolan described it as “a memorial to Bobby and Jeanne for their children, but more than that, a lesson plan in character for their grandchildren.”

Emily Nolan put it this way: “More than anything else, these letters tell a love story. And that’s why they still remain only in the family.”