That’s the obvious conclusion as designer after designer decamps — even just temporarily — to Paris from New York, London or Tokyo. It’s as if the only way to be taken seriously is to show in the French capital (the latest example: Telfar Clemens), as if being a part of the grand finale of ready-to-wear month is the ultimate sign that one has arrived.

“Paris, Capital of Fashion,” at The Museum at FIT, focuses on the spare-no-expense, color-drenched explosion of finery that took off in the Ancién Regime (from the 15th to 18th centuries) and hasn’t stopped since; “French Fashion, Women, and the First World War,” at the Bard Graduate Center Gallery, depicts how the French fashion industry persevered amid hardships and, by war’s end, gave the emerging modern world a pretty good idea of how it would dress.

“Fashion is to France what the gold mines of Peru are to Spain” is the well-known comment by Louis XIV’s finance minister, Jean-Baptiste Colbert, who first organized craft workers into strictly regulated guilds that fended off imports. It was all about “shaping France’s identity and giving France a cultural and economic importance on the international stage,” said Sophie Kurkdjian, co-curator of the Bard exhibition.

The FIT show documents “how Paris acquired and retained its status as our foremost fashion capital,” according to Valerie Steele, the museum’s director and chief curator. The display in the first gallery depicts France “within a global context, in dialogue with other fashion capitals,” she said — engaging in savvy business tactics that have long included not just organized French labor, but the co-opting of foreign talent.

It was, in fact, an Englishman in Paris — Charles Frederick Worth, who transformed couture from a small-scale craft into big business by creating official collections; on display is his 1883 yellow satin ball gown with gold and silver threads and glass beads in a lightning bolt pattern, designed exclusively for Alice Vanderbilt, the wife of Cornelius Vanderbilt II, as a fancy dress costume titled “Electric Light.” A hidden battery allowed her to carry an illuminated light bulb above her head, Statue of Liberty-style.

France was adept not only at protecting its own artisans and attracting other nationalities, but in defanging counterfeiters. To combat the problem, Paris couturiers licensed their designs to other makers instead of standing by while they were copied. A fall 1966/winter 1967 black and white wool tweed Chanel couture suit, collarless, with a pink silk blouse, selling for approximately $400 at the time, is displayed alongside a licensed $40 copy sold by Orbach’s, the moderately priced, now-long-gone New York department store; a Jacques Fath couture evening gown circa 1953, hangs next to a red silk satin dress produced the previous year by Joseph Halpert,” a Seventh Avenue garment manufacturer.

The second gallery at FIT, with a fuller display of couture and confection than the first, takes “a deep dive into the glamour of Paris fashion — how it was constructed and reconstructed over time,” Dr. Steele said. A voluminous petticoat dress from 1755-1760 is shown next to a shorter concoction with a similar silhouette, from the fall 2000 John Galliano for Dior couture “Freud or Fetish” collection. On one side of the Dior dress, there is Marie Antoinette as a faux shepherdess; on the other, she approaches the guillotine.

The standout items in the room include a Madame Grès draped ivory silk jersey gown, circa 1945 and a Rick Owens red stretch Nona dress, shown with red stretch lamb leather boots, also by Mr. Owens, from earlier this year.

So determined was the French cult of the designer to perpetuate itself that, as this exhibition shows, it accomplished the impossible: life after death. Sometimes even long after the deaths of their founders, the houses continued to be animated by new talents such as Claude Montana at Lanvin and, now, Clare Waight Keller at Givenchy.

In the exhibition, to show transitions at work, a black lace and silk dress by Chanel, circa 1926, is next to a 1986 black silk crepe evening dress with embroidered trompe l’oeil jewelry by Karl Lagerfeld, one of Chanel’s successors; and Pierre Balmain’s spring 1954 ladylike Psyche haute couture dress in embroidered lace and silk satin is partnered with a fiercely modern fall 2013 evening dress in beaded black and white raffia and rhinestones by his current successor, Olivier Rousteing.

The idea behind these pairings? “Famous names of fashion can be forgotten unless the name of the house becomes associated with an illustrious successor,” Dr. Steele said.

About three miles north of the FIT, the Bard exhibition underscores something Women’s Wear Daily proclaimed in 1917: “Even while she is crippled through the war, the French couture continued to dictate fashions for the entire world.”

Gathered on the gallery’s three floors are convincing examples of how French fashion moved in new directions during the conflict. This exhibition, a considerably expanded reprisal of the 2017 “Mode & Femmes 14/18” show at the Bibliothèque Forney in Paris, is the first comprehensive view of French fashion during World War I, according to Maude Bass-Krueger, the co-curator and a postdoctoral fellow at Leiden University in the Netherlands. She and Dr. Kurkdjian, a research fellow at the Institut d’Histoire du Temps Présent in Paris, curated both the original show and this expanded exhibition.

Wartime fashion evolved slowly but expeditiously, removing layers and excess for easier wearability as women of all classes went out to work while men fought at the front. Restrictive high waists and narrow hobble skirts were replaced by looser skirts, suits and — shock — trousers and overalls, along with easy-to-wear calf-length dresses, like those in the exhibition designed by Callot Soeurs, Poiret, Lanvin and Vionnet. Pockets, previously separate items worn under or over dresses, were incorporated into designs, and many of them enlarged — sometimes immoderately.

No-nonsense men’s suit-style uniforms for women appeared; an army ambulance driver’s outfit, made in England in 1915, has a fitted jacket but a full skirt. The time was ripe for Chanel and her pared-down men’s wear-influenced styles, such as the 1916 V-neck, sailor-collar silk jersey blouse, its defined waistline cascading into loose pleats, and a 1917 hat, devoid of any frippery save ribbon trim, on display.

In the exhibition’s book-length catalog, Dr. Bass-Krueger’s essay, “Fashion, Gender, and Anxiety,” notes that Frenchmen, especially those at the front, often didn’t welcome the new directions in fashion. Satirical cartoons, postcards and articles — many on display in the exhibition — show how clothing was used, Dr. Bass-Krueger said, “to unmask deep-seated anxiety about what was perceived as a widening rift between men and women over the course of the war.”

The soldiers objected not only to the emerging androgynous designs, but even mourning dresses — seen everywhere following the deaths of more than a million French soldiers — were scorned, the essay noted. (One of the exhibition’s wall labels states that young widows were viewed as “suspiciously ‘available’ and too knowledgeable about sex.”)

But after the war, according to Dr. Bass-Krueger’s essay, “as the black dress evolved into a fashion statement in its own right, the seductive tones of the widow’s dress became its main selling point.” Coco Chanel, for one, took note. Enter the LBD. The deformalization of dress had begun.

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A central idea of the Bard First World War exhibition, said Dr. Bass-Krueger, “is that what we wear tells the story of our times, from the tailored-suit wearing midinettes who went on strike in May 1917 asking for higher pay and a half-day off, to the overall-clad munitionnettes who replaced men in the factories. This narrative continues up to the blue jean and t-shirt-wearing youth at the Global Climate Strike.”

The “Paris: Capital of Fashion” exhibition runs through Jan. 4 at the Museum at FIT, Seventh Avenue at 27th Street; “French Fashion, Women & the First World War” through Jan. 5 at the Bard Graduate Center Gallery, 18 West 86th Street.

An earlier version of this article misquoted a passage from a 1917 article in Women's Wear Daily. The 1917 article said: "Even while she is crippled through the war, the French couture continued to dictate fashions for the entire world." (The remark has been rendered slightly differently in the Bard exhibition.)

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