When I was sick and lay abed,

I had two pillows at my head,

And all my toys beside me lay

To keep me happy all the day.

And sometimes for an hour or so

I watched my leaden soldiers go,

With different uniforms and drills,

Among the bedclothes, through the hills . . .

I was the giant great and still

That sits upon the pillow-hill,

And sees before him, dale and plain,

The pleasant land of counterpane. -- Robert Louis Stevenson

Today children and many adults fight electronic battles of galactic proportions with monsters who clash and clang across video screens.

But in simpler times, before it was possible to wipe out universes, miniature armies fought and died and lived to fight again on battlefields no bigger than a scatter rug. Small surrogate soldiers apparently have always been around. In Egyptian tombs, minute armies guard the dead for eternity. In one ancient Chinese burial hill, full-sized clay figures marched unseen for centuries.

"On Parade, A Cavalcade of Toy Soldiers," an exhibit that opened last night at the National Geographic Society's Explorers Hall, traces the more recent history of this passion. In the exhibit are some 12,000 figures from the collection of millionaire publisher Malcolm S. Forbes.

Yet the battalions are only a striking force of Forbes' immense army of about 80,000 figures, usually set to defending his castle/museum, the Palais Mendoub in Tangier, Morocco. The figures, from the last half of the 18th century, are both exotic and familiar, nostalgic and novel. They look as though the "March of the Toy Soldiers" had suddenly become solidified, or as if some impossibly permissive Santa Claus had suddenly answered 1,000 Christmas letters.

Lest this seem an act of war at the holiday season, a selection is included of peaceful scenes, dioramas of plenty and pleasure. All the groupings are masterfully deployed by Peter Purpura, National Geographic's inspired curator and exhibit designer, who is leaving Washington to set up business in New York as an independent exhibits consultant. Purpura uses Geographic photographs as backdrops in some imaginatively designed display cases.

In a village set, photographs from several places in Europe and Britain were put together for a composite street scene. A grand parade of British regiments and allies, including the colorful Gurkha Rifles and the Egyptian Camel Corps, marches down the street. The Royal Norfolk Regiment is standing around decorating a Christmas tree on one side while a 19th-century German band plays under a nearby gazabo. Sherlock Holmes and Dr. Watson are among the spectators.

Stevenson's poem comes to life in one showcase. Bedouin Arab camel riders, a Boer cotton plantation of pre-1900 South Africa, a Zulu impi (army) with kraal huts, a tiger hunt in India, a Chinese rickshaw with passengers, figures of the Kaiser and King George V of Great Britain, circa 1914, cavort across a child's bed and make forays into the corners. When you look into the people-sized display case, a mirror reflects the viewer's head on the child.

In a tribute to Forbes' ballooning adventures, colorful toy balloons fly against a photographic background of balloon ascensions. The viewer looks down on the "Home Farm," a famous set made in the 1920s, when World War I had made people weary of war, by Britains, the best known British manufacturer. Purpura has devised a circular case so the viewer has the illusion of seeing the world from a balloon. Riding in a balloon basket is a village idiot figure, a character suggested by George V, a rare and expensive model because it was soon dropped from the line on grounds it was tasteless.

The darker side of toys is represented by Hitler in a model of his Wolf's Lair retreat above Berchtesgaden. During World War II, Hitler encouraged the production of toy soldiers made from a composition of sawdust, linseed oil and glue. In another scene, German Gen. George Rommel and his motorized units attack in Libya. Forbes claims he has more Afrika Korps than Rommel, the Desert Fox, had.

The exhibit, put together with the help of Anne and Peter Johnson of London, curators of Forbes' miniatures collection, traces the history of the toys, noting varied manufacturers, as expounded upon in greater detail in their book, "Toy Armies" (Doubleday). The toys originated in the tin mining area around Nuremberg. Pewterers would often create small figures for their children from the snippets left over when they made pots and pans. Johann Gottfried Hilpert is credited as being the first to make commercial toy soldiers, as a tribute to Frederick the Great. Currently, toy soldiers and civilians bring thousands of dollars in the auction houses.

Forbes, at a news conference yesterday, was asked if the soldiers were a good investment. "Well," he said, "I tell my wife what a good investment they are, then I buy lots of them, which drives up the price. And then I say, 'see what a good investment they are.' "

This show, the second drawn from the vast Forbes collections, runs through Easter. An earlier show of Forbes' toy boat collection was also displayed at the National Geographic. CAPTION: Picture 1, Forbes' French Foreign Legion troops aided by colonial forces, fending off an attack on a desert fort; Picture 2, Persian camel archers, circa 1880, fight Alexander the Great at Gaugemala. Photos by Joseph H. Bailey, Copyright (c) 1982, National Georgraphic Society