KITCHENER: The Man Behind the Legend. By Philip Warner. Atheneum. 256 pp. $15.95.

FOR MOST Americans Kitchener is hardly a legend. If they know of him at all it is as the glaring wall- eyed face with pushbroom mustache that dominated those World War I recruiting posters, "Your King and Country Need You."

The poster is famous for what it unwittingly reveals of 1914 Britain, the message being, It's up to you to protect us, the people of power and property. Compare it with Churchill's ringing "We shall fight on the beaches, etc."

In any case, Horatio Herbert Kitchener, 1st Earl of Khartoum and Broome, is remembered today for his picturebook victory at Omdurman, avenging the death of Gordon in the fall of Khartoum and for his amazing creation of a 21/2-million-man volunteer army in 18 months to replace the small professional army wiped out in the battles of 1914.

It wasn't his fault that "Kitchener's Army" was squandered in mindless trench warfare, destroying the nation's best prospects for future officers. "Men volunteered knowing that their expectation of life was probably three weeks from the day they landed in France."

The author, an experienced military historian and senior lecturer at Sandhurst, the Royal Military Academy, writes with devastating authority about the War Office idiocies of that war, allowing so many munitions workers into the army and mishandling production so badly that even late in 1915 Britain was producing 22,000 shells a day compared to 100,000 in France and 250,000 in Germany. And then there were the generals. Just before the disaster of Loos, General French lingered far behind the lines, out of touch. On the second day, in the crisis, he loitered at a dressing station comforting the wounded, a nice gesture but hardly the best place for the commander in chief in a battle that still could have been won.

Warner, who himself fought through World War II, provides one fascinating revelation after another on battles from Omdurman to Gallipoli. He skilfully sketches the situations that created them and even makes sense out of the convoluted Boer War, where again Kitchener's organizing genius was evident if often misunderstood.

Incidentally, he points out, the Dervishes at Omdurman "were not, as they have so often been depicted in films, an undisciplined body of savages armed with spears: they were first-class cavalry and infantry, mostly armed with rifles which they could fire accurately, and precise and accurate in their tactical moves."

Kitchener led that fight personally, "ignoring his staff and issuing orders direct to brigade, even battalion" when the enemy suddenly attacked from two sides. Throughout his life, his tendency to act on his own initiative was to bring great success even as it irritated the more conventional military minds. Tact was not a strong point with this shy, stiff, enigmatic man who, a colleague said, "was never seen to address or even notice a private soldier."

DISMISSED by some as the epitome of the old-school Colonel- Blimp martinet, Kitchener actually was a prescient analyst of world affairs and, according to Warner, might indirectly have prevented or delayed the Russian Revolution had he been given his head. Furthermore, had he become British ambassador to Turkey in 1907, as he wished, "it is highly unlikely that Turkey would have become an ally of Germany in 1914. . . . It was said that his failure to get the appointment was out of the jealousy it provoked in the Foreign Office."

There was a lot of that in Kitchener's life. In spite of it, he appeared to have provided an intelligent, moderate influence for the preservation of the empire.

Warner writes with precision and confidence of the wars and politics of Kitchener's time: he is less successful in bringing his man to life. One wonders if anyone could.

Though Kitchener never married, he was engaged at one point, but the young woman died. One gathers that he was a profoundly repressed person unable to show feeling or to make friends easily. "In spite of his brusque manner and unbending severity, Kitchener had nothing sadistic in his makeup," Warner writes somewhat defensively. "On suitable occasions he liked to be kind."

Warner, in this solidly informative, rather touchingly opinionated book, provides a glimmer of the man concealed by the uniform: He had four spaniels, named "Shot," "Bang," "Miss" and "Damn," a wry comment on the fact that he was an indifferent shot. And this: One day in India a 5-year-old boy, frightened by a loud noise, "at once ran up to Lord Kitchener, seizing his hand and standing close to him for protection -- a gesture which obviously pleased him enormously." Later Kitchener described it as the proudest moment of his life.