The Spanish Civil War pitted the well-equipped and well-trained nationalist armed forces, led by Franco, against the poorly armed and trained troops of the elected Republican Government. It was an unequal contest: Franco's forces were backed by Hitler and Mussolini, and the leftist-liberal Republicans, or Loyalists, were supported by the Soviet Union and the International Brigades, some 40,000 volunteers with little or no fighting experience from 52 countries who wanted to stop Fascism.

Long on idealism but short on military know-how, the Republican cause was doomed, even as it drew such champions as Andre Malraux, Ernest Hemingway, George Orwell, Henri Cartier-Bresson, Tina Modotti, Hans Namuth, David Seymour and Robert Capa. Then as now, some of the most compelling images of that war are Capa's 1936 photograph of a Loyalist falling in battle; Picasso's 1937 painting ''Guernica,'' a wrenching tribute to the victims of German aerial bombing of a Basque village, and Hemingway's 1940 novel, ''For Whom the Bell Tolls.''

But if one could see the Spanish Civil War freed from these familiar images, what would it be? ''The Spirit Lives: Photos From the Spanish Civil War, 1936-39,'' at the Puffin Room in SoHo, comes close to giving a freshly personal perspective to this conflict.

Drawn from the archives of the International Institute of Social History in Amsterdam, most of the photographs in this exhibition have not been shown before in the United States. They survived the war because they were sent to the Paris branch of the Confederacion Nacional del Trabajo, a major labor union and player in the war, then to England and eventually to Amsterdam.

Many of the photographers in ''The Spirit Lives'' bring a so-called snapshot esthetic to their pictures of Republicans and leftists preparing for war or at war. The photographers are all anonymous except for Sam Walters, a veteran of the American contingent of volunteers, the Lincoln Brigade. And the pictures are mostly quiet, taken by people who share a casual familiarity with their subjects. It is that very ordinariness that gives these images their surreal power.

In an overhead shot of a roadside scene, a crowd has gathered around a truck, which has the union's initials on the hood and windshield. Another crowd stands and watches from the pavement, both groups oblivious to a cannon parked nearby. What is going on? ''Distributing arms to the people from a C.N.T. truck, Madrid, 1936,'' the caption says.

A picture of boys marching down the street on a sun-splattered day appear to be playing at war, rifles over one shoulder. But the rifles look suspiciously lethal, and emblazoned on the chest of each boy's sweater is a star, at the center of which is the hammer and sickle insignia. These are ''Young Communists exercising on the streets of Madrid, 1936,'' the caption says.

Two young couples pose for the camera as if out walking in the park, the men in uniform, the women fresh-faced and smiling. They are part of the Garcia Oliver Column setting out in 1936 from their barracks in Barcelona.

In 1931, a year before women first voted in Spain, the Republican constitution introduced political equality for men and women. Early in the war, a few women were leading figures of the Republic, including the fiery Dolores Ibarruri, the Communist leader known as La Pasionaria, who famously told the Republicans on the radio in July 1936: ''It is better to die on your feet than to live on your knees! They shall not pass!''

But this liberating time for women was short-lived. They were soon ordered back home to tend to housework or to work in factories, replacing men who had gone to war. But while it lasted, photographers made many striking images of fighting women.

''Anarchist militiawoman, undated,'' in the exhibition, is a close-up of a determined young woman, her hair tucked into a helmet bearing a skull-and-bones sketch, the shiny barrel of a rifle against one shoulder, her pale eyes steady.

''Militiawoman, Barcelona, July 1936'' shows a different kind of fighter. Here, a young woman, in blouse, skirt and sandals, a purse hanging from a belt, walks cheerfully down the street, toting a rifle.

In an arresting image, three Loyalists lie in wait on the edge of a cliff overlooking a bucolic valley. Two are uniformed soldiers; between them is a woman in a dress and sandals. And in ''Three generations of resistance, undated,'' a grim white-haired woman raises a clenched fist, her daughter and granddaughter following suit.

In the photographs by Sam Walters, his camera is turned on the international contingent and Loyalists waiting to go to war. These pictures have a certain Yankee humor and directness, particularly one of Jack Corrigan. According to the caption, this young man is convalescing, but with his chest bare, a straw hat on his head, a bunch of grapes in one hand, he looks in the pink of health. The caption, however, says he was killed soon after the picture was taken.

Mr. Walters shows a volunteer painting while he waits to be called to battle. A Loyalist peruses an English-language newspaper. And in a poignant photograph, three young women look out a high window protected by a metal grill. They are smiling, carefree, seemingly untouched by war.

The counterpoint of this image, taken by an anonymous photographer, is ''Militiaman and girlfriend saying goodbye, Barcelona, August 1936.'' Photographed from above, this is a spare picture of a couple surrounded by people yet intensely alone, he looking wordlessly at her, she with her eyes cast down.

''The Spirit Lives'' ends with photographs of death and destruction. In a devastating picture that brings to mind the image of the stricken young woman kneeling by the slain student at Kent State, a weeping Spanish woman, her arms outstretched in grief, kneels by a body.

Today, when photography has become, for many artists, a tool for purely esthetic ends, the exhibition at the Puffin Room is a welcome reminder that the camera can be both pitiless and powerful when it records events that forever change people's lives.

''The Spirit Lives: Photos From the Spanish Civil War, 1936-39'' remains at the Puffin Room, 435 Broome Street, near Broadway, in SoHo, through Nov. 29. ''The Spanish Civil War,'' by Abel Paz, published last year by Hazan of Paris and available at $12.95 from D.A.P./Distributed Art Publishers (800-338-2665), includes many of the pictures in the exhibition as well as Mr. Paz's vivid recollections of what he saw and did during one tumultuous and heady week in July 1936, when he was a 15-year-old revolutionary in Barcelona.

Photo: Detail from ''On the Aragon Front'' in ''The Spirit Lives: Photos From the Spanish Civil War, 1936-39'' at the Puffin Room in SoHo. (Puffin Room)