It was the summer of 1946, a year after the end of World War II. Nations were regrouping. Families were reuniting. The baby boom was just beginning.

In the Pacific Ocean's Marshall Islands, at a tiny place called Bikini Atoll, the United States was conducting nuclear tests.

On the other side of the world, a French automotive engineer-turned-fashion designer was in the back room of his mother's Paris lingerie boutique on the verge of dropping a bomb of his own.

Louis Reard was in a dogfight with rival designer Jacques Heim to see who would be the first to introduce a revolutionary two-piece swimsuit.

Heim's creation, which he called the Atome (after the particle), was first shown to beachgoers in Cannes. It was dubbed "the world's smallest bathing suit," according to a history in www.everythingbikini.com.

But Reard, who was working with a mere 27-1/2 inches from a bolt of cloth, took his design a step further -- dropping the bottom half of his two-piece suit below the navel.

Mon Dieu! It was barely a couple of hankies stitched together with string. Nevertheless, Reard was delighted with his provocative invention, which he introduced to the French Riviera (via a skywriter) with this message: "The bikini -- smaller than the smallest bathing suit in the world."

But this was 1946, mind you, and modesty -- not overexposure -- was in vogue. Reard's bikini, which he named after the aforementioned Pacific atoll, blew up in his face.

The problem? The whole bellybutton thing. Navel-baring was a no-no. There was even an edict in Hollywood banning navels from movies.

Vatican leaders called the bikini immoral. The governments of Spain, Portugal and Italy said, "Not on our beaches."

And, much to Reard's dismay, his chosen audience -- the women of the world -- also blushed and said, "No, thanks."

Reard couldn't find anyone willing to showcase his bikini at first. He settled for a nude dancer from the Casino de Paris, Micheline Bernardini, as his bikini fit model.

Indeed, it would require a drastic shift in attitude -- and more fabric -- to market this skimpy suit to the beaches of the world.

"It took about 15 years for the bikini to catch on (in the United States), even though today it's considered ageless and timeless," says Kelly Killoren Bensimon, author of "The Bikini Book" (Assouline, $29.95, 399 pages), a social history of the suit.

"It was scandalous because it was the smallest article of clothing you could wear out in public," Bensimon says from New York. "And yet, women eventually became obsessed with wanting to wear it."

In the 1940s, news of the bikini was hard to come by. There were no cell phones, no e-mail. And newspapers were writing about the evolving atom bomb, not the bikini.

Once news of the suit reached the United States, it quickly was banned on beaches and from the Miss World contest.

It wasn't until 1957, when sexy French actress Brigitte Bardot wore a bikini in the film "And God Created Woman," that women lowered their inhibitions and created a retail market for the suit.

Valerie Steele, director of The Museum at the Fashion Institute of Technology in New York, credits the sexual liberation of the 1960s -- and the subsequent pop-culture movement -- for the mainstreaming boost the bikini needed.

"There were what we call the famous bikinis worn by Ursula Andress ('Dr. No') and Raquel Welch ('One Million Years B.C.') and the popularity of surfer movies with Annette Funicello ('How To Stuff a Wild Bikini')," Steele says from New York.

There was even music, like Brian Hyland's big hit, "Itsy Bitsy Teenie Weenie Yellow Polka Dot Bikini" (1960), which is used today in commercials for Yoplait yogurt.

Steele credits the Brazilians with taking the bikini to even smaller proportions in the 1970s.

"The thong-style suit from 30 years ago is what you see on the beaches of Brazil even today," she says. "And if we go back to France, where the initial uproar began, everyone goes topless, but with a more modest bottom." Bensimon, who also is editor of Elle Accessories magazine, agrees that the bikini celebrates different cultures, even different body types.

"The first models who wore the bikini were extremely voluptuous," she says. "And I've always thought the suit was more sexy on a real body rather than on bones."

Today, age plays a part in whether a woman will wear a bikini, especially in this country. According to Mervyns, suits with more coverage, such as the tankini and a one-piece, are still the most popular.

But in the 18- to 25-year-old group, string bikinis (a triangle top and tie-string bottom) are the top choice of 31 percent of swimwear shoppers. In fact, sales of two-piece suits, which include the bikini, were up 20.5 percent this year over 2005, according to the NPD Group, which tracks consumer spending.

Women spent a little more than $8 billion on two-pieces.

Fortunately, for retailers, the bikini likely will be celebrating 10, 20 -- even 30 years from now. After all, what would Sports Illustrated have done if the bikini ban had held? Cheryl Tiegs in a swim dress?

No doubt, bikinis will always be a loaded topic.

Consider this from humorist Garrison Keillor, who once opined about the teensy suit: "Having a girl in a bikini is like having a loaded pistol on your coffee table. There's nothing wrong with them, but it's hard to stop thinking about it."

(Sources: "The Bikini Book," www.wikipedia.org and www.everythingbikini.com.)

Leigh Grogan can be reached at lgrogan@sacbee.com.